1. Heat oven to 350 degrees F. Line an 8 x 8 x 2-inch baking pan with nonstick foil.
2. In a large microwave-safe bowl, combine butter and chocolate. Microwave for 1 minute. Stir and microwave for an additional 30 seconds. Stir until smooth.
3. Add sugar and espresso powder and mix until combined. Add eggs and vanilla. Stir until eggs are incorporated. Beat in flour and salt until just combined. Fold in mini Kisses and nuts.
4. Pour into prepared pan. Bake at 350 degrees F for 30 to 35 minutes or until toothpick inserted in center comes out clean. Cool 15 minutes. Use foil to lift brownie from pan; cool on a wire rack.
5. Cut into squares. Dust with cocoa and sprinkle with chopped nuts.