- 1/4 cup millet
- 1/4 cup quinoa
- 2 tablespoons amaranth
- 1 cup old-fashioned oats, plus more for topping
- 2 1/4 cups buttermilk, divided, plus more for brushing
- 1 Tbsp. vegetable oil, plus more for pan
- 3 cups whole wheat flour
- 1 cup all-purpose flour
- 2 tablespoons flaxseed
- 1 tablespoon kosher salt
- 2 teaspoons baking soda
- 1/4 cup sunflower seeds, plus more for topping
- 4 tablespoons unsalted butter, cut into pieces
- 3 tablespoons brown rice syrup or mild-flavored (light) molasses
- Mix millet, quinoa, amaranth, 1 cup oats, 1 cup buttermilk, and 1/2 cup water in a small bowl. Cover and let sit 8–12 hours. (Alternatively, bring ingredients to a simmer in a small saucepan over low heat. Remove from heat and let sit until mixture is thick like porridge, about 2 hours.)
- Preheat oven to 350°F. Lightly oil an 8″-diameter cast-iron skillet or cake pan. Whisk whole wheat flour, all-purpose flour, flaxseed, salt, baking soda, and 1/4 cup sunflower seeds in a large bowl. Work in butter with your fingers until largest pieces are pea-size. Make a well in the center and add brown rice syrup, oat mixture, remaining 1 1/4 cups buttermilk, and remaining 1 Tbsp. oil. Mix with a wooden spoon until dough is smooth, homogenous, and still slightly sticky.
- Form dough into a ball and place in prepared pan. Brush with buttermilk; top with more oats and sunflower seeds. Cut a large X into the top and bake until golden brown and an instant-read thermometer inserted into the center of loaf registers 190°F, 55–70 minutes. Let cool in pan.
- Bread can be baked 2 days ahead. Store tightly wrapped at room temperature.