Prepare the Multigrain Base: In a large, heatproof mixing bowl or stand mixer bowl, combine the multigrain flour with boiling water, stirring carefully with a heat-resistant spatula until it forms a thick, porridge-like paste. Add the butter, allowing it to melt and blend in smoothly. Let this mixture rest and cool for about 20 minutes, ensuring it’s warm—not hot—before moving on.
Activate the Yeast: Stir honey into the cooled grain mixture until fully dissolved. Sprinkle in the yeast (and vital wheat gluten, if using) and mix gently. Let it sit for 10 minutes, giving the yeast time to bubble and activate, which ensures a light, airy loaf.
Build the Dough: Gradually add all-purpose flour, about ¼ cup at a time, mixing until a soft dough forms. Knead with the dough hook (or by hand on a floured surface) for 10–15 minutes until the dough is smooth, elastic, and slightly tacky but not overly sticky. Avoid adding excess flour; a soft dough makes a tender bread.
First Rise: Shape the dough into a round ball and place it back in the bowl. Cover loosely with a plate or kitchen towel and let it rise in a warm, draft-free area for 45–60 minutes, or until doubled in size.
Incorporate the Salt & Second Rise: Sprinkle the salt over the dough and knead for another 5 minutes to evenly distribute it. Shape into a smooth ball again, cover, and allow it to rise for a second time in a warm spot for another 45–60 minutes, or until it doubles in size.
Shape & Prepare Loaves: Grease two 9x5-inch loaf pans generously with butter. Divide the dough into two equal portions. Roll each portion into a loaf shape, keeping the top smooth. Lightly brush the tops with water and roll them over rolled oats to coat. Place each loaf, oat-side up, in the prepared pans. Cover and let them rise for the final 60 minutes, until puffy and nearly doubled.
Bake to Perfection: Preheat the oven to 375°F (190°C) halfway through the final rise. Bake the loaves in the center of the oven for 30–35 minutes, until golden brown. The bread is done if it sounds hollow when tapped on the bottom.
Cool & Serve: Remove the loaves from the pans after 5 minutes to prevent steaming. Transfer them to a wire rack to cool completely before slicing. Enjoy fresh or toast slices for a delightful crunch.
