In an electric mixer fitted. with a flat beater, cream butter and cream cheese together until blended. Pour in the flour and beat at low speed until a solid dough is formed, Divide into 48 equal portions or weigh 15 grams per portion.
Press the crust against the bottom and sides of a boat tart molder. Prick the crust bottoms 3 times with a fork. Arrange molders in a jellyroll pan and bake for 15-20 minutes or until the surface feels fairly dry.
Allow crusts to cool briefly then unmold each piece carefully. Arrange the partially baked crusts in a jellyroll pan lined with a sheet of baking paper, Fill with the prepared filling (see instructions below).
To make the filling:
In a thick saucepan, combine condensed milk, yolks, durian jam, and floor. Place over low heat and cook until thick, mixing with a heat-resistant spatula from time to time, Remove from heat and add butter.
Make the tarts:
Divide the filling equally among the pre-baked tart shells. Bake at 350 deg Fahrenheit for 15 minutes or until set.
Allow to cool completely before wrapping individually in food grade cellophane. Makes about 48 durian tarts.