About this recipe:Brazo de mercedes is a type of jelly roll dessert made with a pillowy meringue rolled around a rich custard filling. Although initially I was intimidated by what I thought to be a very complicated process, it turned out to be a pretty simple cake to make.
Use fresh eggs as they whip better. Let egg whites stand at room temperature for about 30 minutes before beating.
Use a copper, stainless or glass bowl. Avoid aluminum bowls as they can turn egg whites to gray.
Use very clean and dry bowls and beaters. Fats or any residue can affect the eggs’ volume. Make sure no traces of yolk get into the whites as they will not expand properly.
Add sugar slowly to not lose volume.
Do not overbeat! You know they have reached stiff peaks when the whipped whites no longer slide around when the bowl is tilted.
To prevent the egg yolks from curdling, make sure to cook the custard over low heat.
For the Custard Filling:
10 egg yolks, beaten
1 (14 ounces) can condensed milk
1 teaspoon vanilla extract
zest of 1 lemon
For the Meringue:
10 egg whites
1 teaspoon cream of tartar
1 cup superfine sugar
¼ cup powdered sugar