In a bowl, sift together the flour and baking powder.In another bowl, cream the butter (or margarine) with three tablespoonfuls of sugar. “Cream” means to beat until light in texture.
Add the flour mixture and the milk alternately into the butter-sugar mixture mixing as you add.
Beat the egg whites until stiff. I did this with an electric mixer but you can use a wire whisk instead if no electric mixer is available. Using a wire whisk to beat the egg whites until stiff will exercise you arm muscles tremendously. I did that a couple of years ago. We just moved to the suburb and most of my kitchen stuff were still in boxes and I couldn’t locate the electric mixer so I used a wire whisk. I did it once and never again.
Anyway… “stiff” means that when you lift the beaters (or wire whisk), stiff peaks are formed on the surface of the egg whites. “Stiff peaks” means the tips do not bow down.
When peaks start to form, sprinkle the remaining two tablespoonfuls of sugar (I usually do this during the “soft peaks” stage) and continue beating until stiff peaks form.
Fold the egg whites into the flour-milk mixture. “Fold” means to mix lightly and carefully carefully so as not to break air bubbles. When you beat the egg whites, the volume triples because of air bubbles which will make the puto light and soft so you do not want to break them.
Fill the puto molds (you can use muffin pans) until about 3/4 full. Top with cheese slices. Thick slices in my case which made my 14-year-old daughter ask why the cheese was “exaggerated”. Well, they used to like lots of cheese on their puto.
Steam the puto for about 20 minutes. If you’re using a metal steamer, you may have to place a towel or muslin (katsa) between the pan and the cover. The cloth will catch the steam and prevent the condensation from falling into the puto which will prevent them from rising properly.
That’s the cooked puto after 20 minutes in the steamer. Cool before removing from the molds because the edges are still a bit wet and soggy while the puto is hot. If you remove them from the molds in that condition, you will disfigure them.