Gradually add the sugar. Continue mixing until texture is semi-firm.
Line a large cookie sheet with parchment paper greased with butter and spread the meringue evenly on top.
Once spread evenly, comb the top of the meringue (I used fork).
Bake at 350 deg F. for 20 minutes or until top of meringue turns light to medium brown.
Remove from oven. Set Aside.
PREPARE THE FILLING (WHILE THE MERINGUE IS STILL IN THE OVEN):
In a sauce pan, combine condensed milk, egg yolks and vanilla.
Simmer over low heat while stirring constantly until mixture becomes thick.
Remove from heat. Set aside.
HOW TO MAKE BRAZO DE MERCEDES:
Sprinkle the confectioners sugar on top of the baked meringue then place wax paper on the top part of the meringue followed by a similar sized baking pan or tray. The meringue should now be in the middle of two baking trays.
Flip the meringue then spread the filling evenly on top of meringue and roll into a log.
Divide the log into two. (Like what I did ont he picture above.)