Dissolve sugar in hot water, allow to cool and add remaining ingredients. Strain egg mixture. Set aside.
Combine flour with sugar. Cut in butter and shortening until mixture resembles coarse meal. Combine eggs with vanilla and add to flour mixture. Mix well. Turn dough onto a lightly floured surface and knead for 30 seconds. Divide dough in 18 pieces and press into 2 1/2" tart pans. Press 1/4" thickness, fluting edge. Arrange tart shells 1" apart on baking sheet. Stir custard mixture, pour into each shell. Bake at 375° for 20 minutes. Serve hot or cool. Tart shells can be purchased in frozen food aisle beside pie shells.