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1
Preheat the oven to 325.
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2
Lightly butter two 10 1/2-by-15 1/2-inch jelly roll pans and line the bottoms with parchment paper.
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3
Butter the paper.
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4
Dust the pans with flour, tapping out any excess.
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5
In a large bowl, using an electric mixer, beat the egg whites with 1/2 teaspoon of the cream of tartar at high speed until soft peaks form.
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6
Add 1/2 cup of the confectioners' sugar and beat at high speed until stiff and glossy.
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7
In another large bowl, beat the egg yolks until pale, about 2 minutes.
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8
Add the flour, 3 tablespoons of cocoa, 1/2 cup of the confectioners' sugar and 1 teaspoon of the vanilla and beat at low speed until combined.
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9
Beat in one fourth of the egg whites, then fold in the remaining whites until no streaks remain.
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10
Pour the batter into the prepared pans and spread in a thin, even layer.
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11
Bake the cakes for 6 minutes, until firm and slightly puffed.
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12
Transfer the pans to a rack and let cool for 5 minutes.
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13
Run the tip of a knife around the edge of the cakes.
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14
Dust the cakes with cocoa and cover each one with a sheet of wax paper slightly larger than the pan.
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15
Invert the cakes onto the wax paper and remove the pans.
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16
Cover the cakes with plastic wrap to keep moist.
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17
In a small bowl, combine 2 tablespoons of very hot water with 2 tablespoons of the granulated sugar and stir until the sugar is dissolved.
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18
Let the sugar syrup cool to room temperature.
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19
In a small saucepan, combine the remaining 1/2 cup of granulated sugar and 1/4 teaspoon of cream of tartar with 3 tablespoons of water and cook over moderately high heat, washing down the sides of the pan with a wet pastry brush and gently swirling the pan, until a deep amber caramel forms, about 6 minutes.
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20
Remove from the heat.
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21
Add 1/4 cup plus 2 tablespoons of the heavy cream and the butter and stir just until combined.
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22
Cook over high heat for 1 minute.
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23
Transfer the caramel sauce to a heatproof bowl and let cool completely.
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24
In a large bowl, using an electric mixer, combine the remaining 1 cup of heavy cream with 1/4 cup of the confectioners' sugar and 1/2 teaspoon of the vanilla.
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25
Beat in the sour cream and salt, then beat until firm peaks form.
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26
Fold in the cooled caramel sauce and refrigerate.
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27
Peel the parchment paper off both cakes and brush the surfaces with the sugar syrup.
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28
Spread the caramel cream over each cake in a thin even layer.
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29
Working with the long side nearest you, roll up each cake, using the wax paper to help you form a tight roll.
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30
Wrap the rolls in the wax paper, transfer to a baking sheet and freeze until very firm, about 2 hours.
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31
Melt the chopped chocolate in a medium microwave-safe bowl.
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32
Whisk in the oil.
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33
Let the glaze cool slightly.
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34
Line a baking sheet with wax paper.
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35
Unwrap the rolls and cut each one into 5 pieces.
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36
Working quickly, dip both ends of each roll into the chocolate glaze, then dip the tops and bottoms, letting any excess glaze drip back into the bowl.
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37
Place the rolls on the prepared baking sheet and refrigerate just until the glaze is completely set.
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38
Serve the yodels cold or at room temperature.
