Brown Sugar Blueberry Banana Bread with Blueberry Butter

Preheat oven to 350F. Spray two 8x4-inch loaf pans with floured cooking spray, or grease and flour the pans; set aside. Bread - In a large bowl, add first 8 ingredients (through nutmeg), and whisk to combine. Add the bananas and stir to incorporate. Add the flour, baking powder, baking soda, optional salt, and fold with spatula or stir gently with a spoon until just combined; don't overmix. Batter is extremely thick. Fold in blueberries with a spatula. Turn batter out into prepared pans, smoothing the tops lightly with a spatula and pushing it into corners and sides as necessary. Bake for about 40 to 45 minutes (if using fresh berries, baking time will likely be reduced), or until the top is domed, golden, and the center is set, and a toothpick inserted in the center comes out clean, or with a few moist crumbs, but no batter. I baked 42 minutes total, and during the last 5 minutes, tented the pans with a sheet of foil so tops wouldn't get too browned before centers cooked through. Baking times will vary based on moisture content of bananas, blueberries, climate, and oven variances. Bake until done; watch your bread, not the clock. Allow bread to cool in pan for about 15 minutes before turning out on a wire rack to cool completely before slicing and serving. While bread cools, make the Blueberry Butter. Blueberry Butter - In a small bowl, combine the butter, blueberries, and whip vigorously with a spoon to combine. Optionally, instead of blueberry butter, try Strawberry Butter, Honey Butter, Cinnamon-Sugar Butter, or Vanilla Browned Butter Glaze. Bread will keep airtight at room temperature for up to 1 week, or in the freezer for up to 6 months. Blueberry butter will keep airtight in the fridge for up to 1 week.