Microwave chocolate and butter, stir until smooth, set aside. Beat eggs, sugar, espresso powder, vanilla, almond extract and salt in large bowl of electric mixer at high speed 10 minutes. While egg mix is beating, line a 13x9” pan with foil and brush with butter or spray with Pam. Unwrap mints (put about 15 aside; you won't need them all). When egg mix has hit 10 minutes, reduce speed to low; add chocolate mixture (which may still be warm). Beat just until mixed. Add flour; beat on low speed just until mixed. Remove bowl from mixer; stir in nuts. Pour half of mixture (about 3-1/2 Cups) into the pan. Place 1 layer of mints, touching each other and edges of pan, all over batter.
Pour remaining chocolate mixture over; smooth top. Bake at 425° F. until brownies have firm crust, but center is wet when tested with toothpick, about 30 minutes. You may have some burned edges, which you can cut off later. Cool on wire rack. Remove pan and foil lining, and refrigerate several hours or overnight before cutting into bars. Pack in airtight box. These freeze well.