HEAT oven to 350ºF.
PREPARE 1 T DISC in large mug; use same mug to prepare remaining T DISCS. Refrigerate 15 min. or until cooled.
MIX flour, baking powder and salt. Beat butter and sugar in large bowl with mixer until light and fluffy; blend in egg and coffee. Gradually beat in flour mixture. Stir in bananas.
SPREAD onto bottom of 13x9-inch pan sprayed with cooking spray; sprinkle with nuts and chocolate chips.
BAKE 32 to 34 min. or until toothpick inserted in center comes out clean. Cool completely.