Puree the beans with the oil in a blender. Add the eggs, cocoa, sugar, and vanilla. Blend until smooth. Add the flour, baking powder, and salt to the blender and pulse until just incorporated. Pour batter into baking pan. Top with chocolate and/or toffee chips (optional.) Bake at 350 degrees for about 20 minutes. Let cool at least 15 minutes before cutting and removing from the pan.