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1
Preheat oven to 325u00b0F.
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2
Oil and flour a 9-inch springform cake round.
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3
Cut a piece of wax paper or parchment to fit inside the bottom of the pan, place the paper in the bottom of the pan.
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4
In a double-boiler on gentle heat, melt the butter and chocolate together until smooth.
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5
Set aside to cool slightly.
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6
In a clean mixing bowl (make sure there is no oil residue on the bowl or mixer attachments) beat the egg whites until they become cloudy and frothy; about 30 seconds.
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7
Continue beating while adding the brown sugar and cream of tartar.
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8
Beat until stiff peaks form- be careful not to over beat--this is most important!
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9
If the eggs curdle, throw them away and start over with new egg whites, seriously.
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10
Whisk the egg yolks and vanilla into the melted chocolate mixture in a large mixing bowl.
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11
Gently fold the egg whites into the chocolate (start by folding in about 1/3rd of the whites, then gently fold in the remaining whites), the mixture should end up fluffy and light.
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12
Pour into the prepared pan.
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13
Wrap the bottom of the pan with foil and place the pan in a deep cooking sheet with about 1/2 to 1 inch of water in it.
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14
Bake the cake for about 60-70 minutes or until it passes the toothpick test.
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15
Remove cake from oven and allow to cool for about an hour.
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16
Gently run a knife around the edge of the pan, and then carefully invert the cake onto a flat plate or other surface.
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17
Remove the paper from the bottom (now the top) of the cake.
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18
Invert again onto the final plate for displaying the cake.
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19
The cake can be eaten right away but it may fall slightly when it is cut- for best results, it should be refrigerated for at least 6 hours before serving.
