Set a heatproof glass bowl over a pot of simmering water. Do not let the water touch the base of the bowl. Add the butter, milk, cream cheese and oil and stir until melted and smooth. Turn off heat and let mixture cool. Some bits of the cream cheese may still be present. This is fine as they will get mixed in once the flour is added.
Add the egg yolks to the mixture and mix until uniform. Combine the flour and the baking powder and add to the mixture as well. Stir until smooth. Preheat oven to 350 F.
While mixing in the flour mixture, start to beat the egg whites using high speed on a stand or hand mixer. Once the egg whites are frothy,add in the cream of tartar.
Once soft peaks form, Gradually add the sugar until the egg whites form stiff peaks.
Stir a little amount off the egg whites to the yolk batter to thin the yolk batter a little bit. Gently fold the remaining egg white mixture to the egg yolk mixture in gradual amounts, being careful not to deflate the egg whites too much.
Place cupcake molds on a large rimmed baking sheet. Spoon batter into cupcake molds until about ¾ full. Fill the rimmed baking sheet with water, up to half an inch from the bottom of the molds.
Bake for 22- 25 minutes ( for the large molds)* or until a toothpick inserted into the middles of the cakes comes out with little bits of moist crumbs. Tops should be light golden brown. Turn off the oven.Open the oven door and let mamon stay inside for about three minutes. This prevents them from shrinking too much.
Take out from the oven and let cool, then unmold if desired.