In the bowl of a stand mixer fitted with the dough hook attachment, stir together flours, 1 cup warm water, warm milk, honey, butter, salt, yeast, and onion powder. Beat at medium speed until smooth and elastic, about 5 minutes, stopping to scrape sides of bowl. Add sunflower seeds, 2 tablespoons poppy seeds, and flax seeds, beating until combined.
Turn out dough onto a lightly floured surface, and knead 5 times. Shape dough into a ball. Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Cover directly with plastic wrap, and let stand in a warm, draft-free place (75°) until doubled in size, about 1 hour.
Preheat oven to 375°. Divide dough into 16 pieces; shape into balls. Place . inch apart in a 12-inch cast-iron skillet. Cover and let stand in a warm, draft-free place (75°) until doubled in size, about 15 minutes.
In a small bowl, whisk together egg and 1 teaspoon water. In another small bowl, combine sesame seeds, fennel seeds, garlic salt, onion flakes, sea salt, and remaining ½ tablespoon poppy seeds. Brush rolls with egg wash; sprinkle with seed mix.
Bake until golden brown, about 25 minutes. Let cool for 10 minutes. Serve with Green Onion Spread.
Recipe by Southern Cast Iron at https://southerncastiron.com/everything-rolls/