Brazo de Mercedes

Instructions

1. Mix egg yolks, milk, vanilla extract, and lemon zest. Stir until well-blended.
2. Place in a double boiler and cook, stirring often, for about 30 to 40 minutes or until mixture thickens into a spreadable paste. Transfer custard into a bowl and cover with wax paper until ready to use.
3. Preheat oven to 350 F.
4. Mix egg whites and cream of tartar. Using an electric mixer, beat at low speed.
5. As the egg whites start to turn opaque and begin to fluff into a thick foam, gradually Add sugar in small amounts and continue to beat while gradually increasing the speed of the mixer until stiff peaks form. The whipped whites will be smooth and glossy, with no sugar grains.
6. Line a 14 x 16 baking sheet with parchment paper and lightly grease the surface of the paper. Set it aside.
7. Transfer meringue onto the prepared baking sheet and, using a spatula, spread evenly across into about ¼-inch thick.
8. Bake in the oven for about 20 minutes or until the meringue is set and the top has turned light brown. Remove from oven and allow to cool.
9. Light dust top of the meringue with powdered sugar. using fine-mesh sieve
10. Place another layer of greased wax paper and another baking sheet over the meringue. Gently invert the meringue onto the new baking sheet and peel the wax paper on top.
11. Spoon custard on top and spread evenly on the cooked meringue, leaving about ¼ without filling.
12. Starting on the filled side, carefully roll meringue into a log.
13. Cover both ends of the Brazo de Mercedes with wax paper and chill in the refrigerator for about 1 hour.
14. To serve, cut into desired thickness.
15. Combine the ingredients until well-blended BEFORE placing on the flame, as the heat can cook the yolks into scrambled eggs and turn the mixture lumpy.
16. For a silky and smooth texture, cook the custard mixture low and slow. High heat can curdle the yolks. Tend to custard and stir regularly to prevent lumps.
17. Cook the custard until thick but spreadable. Remember that the mixture will continue to thicken as it cools. Lightly press plastic film on the surface of the cooked yema to keep it from drying out.
18. Older egg whites create more volume, but fresh eggs have a more stable foam.
19. Let egg whites stand at room temperature for about 30 minutes before beating for maximum volume.
20. Skip aluminum bowls, as they can turn egg whites into gray or plastic bowls, which usually have hidden traces of fat or grease that can spoil the meringue and keep it from stiffening up. Chefs prefer to use copper bowls as the chemical reaction between copper and the egg whites produces a more stable foam, but if you don't have that, a stainless or glass bowl is okay.
21. Use very clean and dry bowls and beaters. Fats or any residue can affect the eggs' volume and cause the meringue to deflate.
22. Make sure no traces of yolk get into the whites, as they will not expand properly. Crack the eggs on the counter and not on the edge of the bowl to reduce the chance that a shard of the shell will puncture the yolk.
23. Add sugar gradually to the egg whites to avoid losing volume.
24. Do not overbeat! You know they have reached stiff peaks when the whipped whites no longer slide around when the bowl is tilted. Properly-whipped egg whites should look shiny and moist.