1. Melt chocolate pieces in a small metal bowl placed in a skillet of hot (not boiling) water; remove from skillet and let cool.
2. Sift flour, baking powder, salt and baking soda onto wax paper.
3. Beat shortening and brown sugar until fluffy in a large bowl with electric mixer at medium speed; beat in eggs until smooth.
4. Stir in flour mixture until smooth with a wooden spoon; blend in melted chocolate, nuts, bananas and lemon rind until well blended.
5. Drop by rounded teaspoonfuls, 2 inches apart, onto lightly greased cookie sheets.
6. Bake in hot oven (400°) 10 minutes, or until tops spring back when lightly touched with fingertip. Remove from cookie sheets to wire racks with wide spatula or pancake turner. Cool completely before storing in metal tin between layers of wax paper or transparent wrap.