Step 1

Preparation Preheat oven to 375°. Lightly butter an 8x4" loaf pan and line with parchment paper, leaving generous overhang. Place yeast in a medium bowl (or the bowl of a stand mixer) and add 1 cup warm water; stir to dissolve yeast. Add cornmeal, molasses, hemp seeds, nigella seeds, golden and brown flaxseed, poppy seeds, salt, 2 cups flour, and 2 tablespoons unsalted butter. Using a wooden spoon (or dough hook if using stand mixer), mix until no dry spots remain.

Step 2

Turn out dough onto a lightly floured surface and knead until dough is smooth and elastic, 10–15 minutes (alternatively, mix in stand mixer on medium speed 8–10 minutes). Lightly butter a medium bowl. Transfer dough to bowl and turn to coat. Cover with plastic wrap and let rise in a warm, draft-free spot until almost doubled in size, about 1 hour.

Step 3

Punch down dough to deflate; cover. Let rise again until about doubled in size, about 1 hour.

Step 4

Turn out dough onto a lightly floured surface and pat into an 8x4" rectangle. Starting at the short side farthest from you, roll up dough, pinching the seam as you go, to create a tight roll. Pinch seam to close; tuck ends under and pinch to seal. Place seam side down in prepared pan and cover with plastic. Let dough rise until it crests the top of the pan and springs back slightly when pressed, about 1 hour.

Step 5

Brush top of dough with egg. Bake, rotating halfway through, until bread is baked through and top is a deep golden brown, 45–50 minutes. Let cool slightly in pan on a wire rack before turning out. Let cool before slicing (if you can wait that long). Serve with salted butter. Do ahead: Bread can be made 5 days ahead. Store tightly wrapped at room temperature.