Add bread flour, rye flour, cocoa, brown sugar, salt and instant yeast to a large bowl. Whisk to combine. Set aside.

In a large measuring cup whisk milk and molasses together until combined.

Pour the milk mixture and 4 tablespoons of melted butter into the dry ingredients and mix until combined and a rough dough is formed. I find it easiest to just use my hands here. Cover the bowl and let the dough rest for 30 minutes.

Fold the dough (using damp hands) by stretching up each side of the dough and folding it into the center, for a total of four folds. The dough will be fairly stiff!

Cover the bowl and let the dough rest for another 30 minutes.

Repeat the folding process from step 4. Cover and let the dough rise until doubled in size about 2-2 ½ hours.

Grease a 9x13 inch baking dish (preferably metal) with butter all over. Portion the dough into 24 (50 gram) pieces. Lightly flour your work surface and hands and form each piece into buns by cupping your hand over the dough and using a quick circular motion to form a tight ball.

Place the rolls into the prepared pan in a 4x6 fashion. The rolls will just barely touch. (See note about making these a day ahead*)

Cover the pan with plastic wrap and let the rolls rise again until they are puffed and fit snugly in the pan, 2-2 ½ hours. The won't quite double in size.

Preheat the oven to 400F. Whisk the egg with 1 tablespoon of milk until combined. Brush the rolls with the egg wash and sprinkle with oats and flake salt.

Bake for 28-35 minutes until the rolls are puffed and the tops are golden.

While the rolls bake prepare the honey butter: Place the butter, honey, salt and pepper in a small bowl, whip with an electric hand mixer until combined and fluffy, 4-5 minutes. Set aside. These rolls are also great with just salted butter as well!

Let the buns cool 5-10 minutes, brush them with more melted butter and enjoy them warm with the hot honey butter or salted butter on the side.