Banana Nut Muffins

Name: Banana Nut Muffins
Ingredients: 2 to 3 ripe bananas , thoroughly mashed (about 1 1/4 cups mashed ); 1/2 to 3/4 cup (100 to 158g) sugar; 1 large egg; 1 tablespoon strong brewed coffee or espresso, or 1 big pinch instant coffee granules mixed with 1 tablespoon water (optional); 1 teaspoon vanilla extract; 1/3 cup (76g) melted butter (salted or unsalted); 1 1/2 cups (207g) all-purpose flour; 1/2 teaspoon baking soda; Pinch salt; 1 cup (123g) chopped walnuts or pecans ( toasted or raw)