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1
Position a rack in the lower third of the oven and preheat the oven to 400u00b0 F. Line the bottom (not the sides) of a 12 by 16-inch half sheet pan (or 11 by 17-inch jelly roll pan) with parchment paper.
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2
Whisk the flour with the baking powder. Sift the mixture three times and return it to the strainer set over a bowl.
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3
Whip the eggs, yolks, sugar, and vanilla in the stand mixer at high speed for 2-4 minutes until the batter is light-colored, tripled in volume, and when the whisk is lifted the mixture falls in a thick fluffy rope that dissolves slowly on the surface of the remaining batter foam.
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4
While the eggs are beating, heat the milk and butter in a small saucepan until it the butter is melted and the mixture is extremely hot to the touch. (It must be very hot when you add it to the batter.)
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5
Remove the bowl from the mixer. With the strainer or sifter, sift one-third of the flour over the eggs. Fold with a large rubber spatula until the flour is almost blended into the batter. Repeat with half of the remaining flour. Repeat with the rest of the flour. Pour all of the hot milk mixture over the batter and fold gently but authoritatively, scraping batter up from the bottom of the bowl and rotating the bowl until the milk and butter are incorporated. Scrape the batter into the pan, and spread it evenly, taking care that the batter in the center is not deeper than than the batter at the edges (or your sponge sheet will over cooked and/or dry at the edges).
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6
Bake 10 to 12 minutes until the cake is golden brown on top and springs back when gently pressed with fingers.
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7
Remove the cake from the oven and run a slim metal spatula around the edges to detach the cake from the pan. Cover the pan with a sheet of parchment paper longer than the pan at both ends. Hold the ends of the paper and the pan together and invert the whole business onto the counter (or on another baking sheet-but not on a rack)-so the top of the cake rests directly on the parchment. Leave the pan on top so that the cake steams a little as it cools. The top of the cake will stick to the parchment-this is correct. Let the cake cool completely while you make the cranberry raspberry spread.
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8
Make cranberry-raspberry spread: Put the cranberries in a small saucepan with 1/4 cup sugar. Cover and cook until about 2/3 of the berries are burst (4-5 minutes). Scrape the mixture into a medium coarse strainer with the raspberry or cherry preserves. Mash and press as much of the mixture through the strainer as possible, using a rubber spatula. This will take some effort-keep on mashing and rubbing into the strainer. Scrape the strained mixture from the underside of the strainer into the bowl. Continue to press the mixture, even with your fingers, until there's only 2-3 tablespoons of dry cranberry skins and raspberry seeds left behind to discard. You should have about 2/3 cup strained cranberry spread. Set aside.
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9
To assemble and freeze the cranberry-raspberry jelly roll (for lining for the bombe mold): Tear off a sheet of foil the size of the sponge sheet and set it on the counter next to the sponge. Lift the pan off of the sponge sheet and peel off the parchment liner. Using the parchment under the cake, flip the cake over onto the foil. Peel the parchment from the cake, taking all or most of the skin off of the cake as well. If any of the skin remains, remove it with a knife.
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10
Spread all of the cranberry-raspberry in a very thin even layer over the sponge sheet. Starting with one long edge, use the foil underneath the cake to help roll the cake as tightly as possible to form a 16 or 17-inch jelly roll. To tighten a jelly roll, imagine it as rolling a sleeping bag as tightly as possible so that you can squeeze it back into its impossibly small bag. Start with the sponge sheet on a piece of foil on the counter with one long side facing you. Start at the edge of the cake thats nearest you-and using the foil under the cakes as necessary, fold the least amount of cake possible over itself to start the roll, and keep the roll as round and tight as possible as you roll the cake away from you. When the roll is complete, squeeze and tighten it as follows: Roll the entire jelly roll back towards the center the foil. Pull the far end of the foil towards you and over the jelly roll to cover it. Hold a ruler or straight edge on top of the foil against the bottom of the jelly roll. Use your other hand to anchor the foil under the cake against the counter so it won't slide while you press the edge of the ruler away from you, against the top foil (which should be free so it will slide forward) as you tighten the jellyroll inside the foil.
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11
Wrap the jelly roll tightly in the foil. Freeze for several hours or overnight for easiest handling. You can do this days or weeks in advance!
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12
To line the bombe with jelly-roll slices: Have a 6-cup half dome shaped bowl or bombe mold at hand (mine is 7 1/4 inches in diameter and 3 1/2 inches deep). There is no need to line it or grease it.
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13
Remove the frozen jelly roll from the freezer and unwrap it. Without thawing, trim ragged ends if necessary (and reserve the trimmings). Use a sharp serrated knife to cut slices 1/4 inch thick. Line the mold with slices as follows: place 1 slice in the center of the bottom of the mold. Next fit 7 (or more, as needed) slices around the center slice, pushing and fitting them together (assertively!) so that no space whatever is left between them (take this seriously or you will end up with mousse showing between the jelly-roll slices. Fit the next 9 or more slices around the mold, starting up the sides. Finish by fitting the next 10 or so slices to completely line the mold, always pushing and fitting to eliminate any space between slices. Push the last slices even with the rim of the mold if possible, or trim them so that they are flush. Reserve, wrap and freeze all trimmings and extra slices. Set the lined mold aside while you make the mousse.
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14
To make the mousse and fill the mold: Put the white chocolate, water and kirsch in a medium stainless steel bowl. Bring 1 inch of water to a simmer in a wide skillet. Turn the heat off under the skillet (or remove it from an electric burner) and wait 30 seconds, then set the bowl of chocolate directly into the hot water. Stir constantly until the chocolate is melted and smooth. Remove the bowl from the water and let the chocolate mixture cool until it is 85F-slightly cool when you dab a little on your lip. If the chocolate is too cool or cold, the mousse will be grainy, if it is hot, it will melt the whipped cream you are going to fold into it.
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Just before the chocolate is cool enough, whip the cream only until it is thickened and barely being to hold a share-when you tilt the bowl the cream should flow to one side, fluffy but still pourable and not at all stiff. Scrape the cream into the bowl of chocolate (not vice versa!) and fold carefully but quickly just until the two are incorporated. The mousse should seem far too soft to set-but it will firm up as it cools. Immediately (before the mousse even thinks about starting to set) scrape it all into the lined bomb mold and spread it evenly.
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16
Remove the remaining jelly-roll slices and trimming from the freezer. Set aside just enough slices to completely cover the top of the mouse if placed tightly together- do this by laying slices on a piece of parchment and then pushing the edges together to form a round layer the same diameter at the bomb mold or bowl-but don't put them into the mold yet.
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17
Dice any remaining slices and trimming with a sharp knife. Scatter the dice evenly over the mousse. Now (finally), fit the slices assembled into a layer over the dice cake pieces to form the bottom layer of the dessert. Place a cardboard round or flat plate smaller than the diameter of the mold inside the mold and press firmly to level and compact the bombe. Wrap and refrigerate the bombe for at least 6 hours before unfolding and serving. The bombe may be completely to this point up to 36 hours in advance.
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18
To unfold and finish the bombe: Invert the mold and rap the edges sharply on the counter to release the dessert onto a cake circle or cookie sheet. Simmer trained apricot preserves in a small saucepan for 2-3 minutes to make a glaze. Use a pastry brush to paint the entire dessert with a very thin coat of glaze. Touch the bottom edges of the bombe with minced pistachios. Transfer to a serving platter. Refrigerate until serving.
