Heat oven to 350 degrees F; coat a 9 x 13-inch pan with nonstick spray.
Blend drained beans and 2 egg whites or 1/3 of 1/2 cup egg substitute) in food processor or blender until smooth. Set aside.
Place chocolate and lite butter in small microwave safe bowl. Microwave for 60-90 seconds. Stir every 30 seconds until smooth. Set aside.
Combine bean puree, sugar, flour, coffee powder and remaining egg whites or egg substitute in a mixing bowl. Beat until well combined. Blend in melted chocolate, pour mix into pan, sprinkle with walnuts. Bake 30-35 minutes.