Preheat oven to 350°.
Coat bottom of a 9-inch square baking pan with cooking spray.
Combine coffee granules and 1/4 cup hot water, stirring until the coffee granules dissolve.
Combine butter and semisweet chocolate chips in a small microwave-safe bowl. Microwave at HIGH for 1 minute or until butter melts; stir until chocolate is smooth.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, sugar, unsweetened cocoa, baking powder, and salt in a large bowl, stirring with a whisk. Combine coffee mixture, butter mixture, vanilla extract, and eggs in a medium bowl, stirring with a whisk. Add coffee mixture to flour mixture; stir just until combined. Spread evenly into prepared pan. Sprinkle evenly with toffee chips. Bake at 350° for 22 minutes. Cool on a wire rack.