To prepare cupcakes, place 12 muffin cup liners in muffin cups; coat liners with cooking spray. Set aside.
Place granulated sugar and 1/4 cup butter in a large bowl; beat with a mixer at medium speed until well blended (about 4 minutes). Add eggs, 1 at a time, beating well after each addition.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking soda, and 1/4 teaspoon salt, stirring with a whisk. Combine banana, yogurt, and 1 1/4 teaspoons vanilla, stirring well. Beating at low speed, add flour mixture and banana mixture alternately to sugar mixture, beginning and ending with flour mixture. Spoon batter into prepared muffin cups (cups will be full). Bake at 350° for 20 minutes or until a wooden pick inserted into center of 1 cupcake comes out clean. Remove cupcakes from pan; cool completely on a wire rack.
To prepare frosting, place 1/3 cup butter, liqueur, and 1/4 teaspoon vanilla in a large bowl; beat with a mixer at medium speed until smooth. Gradually add powdered sugar and 1/8 teaspoon salt, beating just until smooth. Spread frosting evenly over cupcakes; sprinkle evenly with almonds.
Didn't make the icing (sprinkled turbinado sugar on top before baking) but the cupcakes are so delicious I'm giving five stars even w/o icing. I did add 1/4 tsp. almond extract, a dash of nutmeg, and used 50/50 white & whole wheat flour, otherwise no changes. Fluffy, complex in flavor, and delicious with ice cream or plain! Might add chopped walnuts next time. Did need 5 extra minutes in the oven.