Combine cracker crumbs, butter, and 2 tablespoons sugar; mix well. Fill each of 48 miniature 1 3/4-inch muffin tins with 1 1/2 teaspoons crumb mixture. Press mixture firmly into bottom and sides of muffin tins.
Combine cream cheese and 1/4 cup sugar in a medium mixing bowl; beat well. Add egg yolk and 1/4 teaspoon vanilla, beating until well blended. Beat egg white (at room temperature) until stiff peaks form. Fold into cheese mixture. Spoon 1 teaspoon cheese mixture into each shell. Bake at 350° for 15 minutes. Remove from oven.
Combine sour cream, 1 tablespoon sugar, and 1/4 teaspoon vanilla; mix well. Spoon 1/2 teaspoon topping on each tart. Bake at 350° for 5 minutes. Remove from tins; cool on wire racks.