Arroz con leche was my favorite dessert as a child. This is a subtly sweet twist on my New Mexican grandmother's traditional "sweet rice." The fluffy egg white topping comes from grandmother's original recipe; the lemon zest and rum-soaked raisins are my additions from other traditional Mexican ones. —gabrielaskitchen
(Optional) Heat rum in a small saucepan remove from heat and add raisins and stir. Set aside.
Place milk, water, rice, and lemon zest in a medium heavy-bottom sauce pan. Bring to a gentle boil, once boiling, reduce heat, cover and simmer for 25 to 30 minutes, stirring occasionally until the rice is tender. Remove from heat.
Add the can of evaporated milk and sweetened condensed milk. Place back on low heat and stir occasionally until milk has thickened slightly, for about 5 minutes. Make sure you DO NOT BOIL the rice pudding at this point. If desired, add raisins. Remove from heat and keep covered with a lid.
Meanwhile, in a large bowl, whisk whites until frothy (nearing soft peaks). Pour frothy whites atop the rice pudding and cover with lid. The heat from the just cooked rice will cook the fluffy whites. [Editors' note: We folded the whites into the pudding at this point using a rubber spatula.]