Seeded Whole Grain Soda Bread

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.