1) Preheat the oven to 350°F. Lightly grease a 9" x 5" loaf pan.
2) In a large bowl, stir together the oil or melted butter and sugar.
3) Add the eggs, mixing until well blended.
4) Add the mashed banana, baking mix, baking soda, cinnamon, and nutmeg all at once, mixing until blended.
5) Stir in the walnuts.
6) Spoon the batter into the prepared pan. Sprinkle with sparkling sugar, if desired.
7) Allow the batter to rest 10 minutes.
8) Bake the bread for 45 minutes, then gently lay a piece of aluminum foil across the top, to prevent over-browning.
9) Continue to bake until the top springs back and a toothpick inserted into the center comes out clean or with a few wet crumbs clinging to it, an additional 20 to 25 minutes.
10) Allow the bread to cool for 10 minutes in the pan. Run a table knife around the edges, turn it out of the pan, and cool completely on a rack.
Yield: 1 loaf, about 16 slices.