To prepare the pastry, lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, 1 1/2 tablespoons sugar, 1/2 teaspoon salt, and the baking powder in a food processor; pulse 3 times. Add the shortening; pulse 4 or 5 times or just until combined. Place flour mixture in a bowl. Gradually sprinkle ice water over the flour mixture; toss until moistened. Turn dough out onto a lightly floured surface, and gently knead 3 to 4 times. Press mixture into a 4-inch disk. Place between 2 sheets of plastic wrap; chill 30 minutes.
Preheat oven to 375°.
Roll the dough into an 11-inch circle; remove plastic. Cut dough into 18 circles using a 2 1/2-inch cutter. (Reroll any of the remaining pieces of dough.) Fit dough into miniature nonstick muffin cups coated with cooking spray. Gently press dough into bottom and sides of cups.
To prepare filling, divide chocolate and pecans evenly among muffin cups. Combine 2 1/2 tablespoons sugar and next 6 ingredients (through dash of salt) in a small bowl; stir well with a whisk. Divide sugar mixture evenly among cups. Bake at 375° for 15 minutes or until pastry is lightly browned and the filling is set. Run a knife around each tartlet; remove from pan. Lightly brush tartlets with 2 teaspoons bourbon, if desired. Cool completely.