2 pieces store-bought oval llanera (2 cups capacity aluminum molds).
Put 1/3 cup sugar per mold. Put mold on top of medium fire (use a pot holder) to tilt pan until sugar is dissolved and caramel colored. Repeat with second mold. Pour filling on each. Cover tightly with doubled-up foil with a half-inch overhang. Seal well by crumpling with your fingers. Water from steamer will prevent the center of flan from getting firm. Put on top of steamer over simmering water (do not fast-boil as this will create holes or rough-textured flan). Steam 35 to 40 minutes. Cool. Remove foil. Loosen sides with a knife or metal spatula. Put a deep plate on top and invert.
Mix in a bowl with a wire whisk then strain: 12 egg yolks (3/4 cup egg yolks), 2 cans condensed milk (3 cups) 1 tsp. vanilla extract or ube or pandan flavor.
Note: Another way to serve this is to put some cooked flan in an ice cream glass. Top with crushed ice and some flan. Serve with milk on the side.