Pour melted butter into 2-pound coffee can; swirl to butter sides. Sprinkle with half the nuts. Mix brownies according to the package directions. Pour half the batter into coffee can, covering nuts evenly. Add remaining half of nuts, then batter.

Place can in Crockpot. Cover top of can with 8 paper towels. Cover and bake on HIGH setting for 3 hours. Do not check or remove cover until last hour. (If using Bread 'n Cake Bake pan, bake in covered pan on HIGH setting for 2 to 3 hours.)

Remove can and discard paper towels. Let stand 5 minutes. Unmold and serve warm.