Preheat oven to 350 degrees F. Grease and flour a 9x13-inch baking pan and set aside.
In a large bowl, whisk together the flour, baking powder and salt; set aside.
Beat egg yolks with 3/4 cup sugar on high speed until yolks are pale yellow.
Stir in milk and vanilla.
Pour the egg yolk mixture over the flour mixture and, using a rubber spatula, gently fold together until thoroughly combined.
Clean out the bowl and the whisk, or use separate clean bowl.
Add the egg whites to the bowl and whisk at high speed until soft peaks begin to form. With the mixer still running, pour in the remaining ¼ cup of granulated sugar and beat until the egg whites are stiff but not dry.
Gently fold the egg whites into the batter until just combined.
Pour the batter into the prepared pan and smooth the surface with a spatula.
Bake for about 35-40 minutes, or until a toothpick inserted in the center comes out clean and top is golden brown.
Allow to cool completely.
Once cooled, combine cream (1/2 cup), Rum Chata, evaporated milk, and sweetened condensed milk and whisk to combine.
Using a fork, pierce the surface of the cake all over.
Slowly pour milk/Rum Chata mixture over cake. Some recipes recommend pouring all but 1 cup over the cake, but I used it all. Pour slowly and to your liking.
Let the cake absorb for 30 minutes, then make the frosting.
to make the whipped cream frosting:
Whip together the heavy cream, powdered sugar, and Rum Chata on high with whisk attachment of an electric mixer until stiff peaks form.
Spread evenly over cake.
Slice and enjoy!
I found this cake best chilled overnight, letting the flavors develop, but at the very least, try to chill at least 2 hours before serving.