Lightly spray twenty-four 1-3/4-inch muffin cups with nonstick spray coating; set aside.
For pastry, beat 1/3 cup butter, 1/4 cup sugar, vanilla, and salt in a small mixing bowl with an electric mixer until combined. Beat in egg yolk; stir in 1 cup flour. Divide into 24 equal portions. Shape each portion into a ball. Place each ball in a prepared muffin cup. Press dough evenly against the bottoms and up the sides of cups.
Sprinkle raisins in bottoms of pastry lined cups. For the spiced streusel, combine 1/4 cup all-purpose flour, brown sugar, ground cinnamon, ground nutmeg, and ground ginger in a small mixing bowl. With a pastry blender or fork, cut in 1 tablespoon butter until mixture resembles coarse crumbs. Divide half of the spiced streusel among cups (about 1/2 teaspoon per cup). Combine hot water and baking soda in a small bowl. Stir in molasses and egg. Spoon about 2 teaspoons of the filling into each cup. Sprinkle with remaining streusel.
Bake in a 350 degree F oven for 25 to 30 minutes or until pastry is golden and filling is puffed. Cool 5 minutes in the pan. Carefully remove tarts from pans and cool on wire racks. Makes 24 tarts.