Preheat the oven to 375 degrees. Stir the lemon juice into the milk and let sit until ready to use.
In a large bowl, combine both flours, the oats, sugar, salt, baking powder, baking soda, rosemary (crushed or chopped), and black pepper. Stir until combined.
Place the butter in a small pot and melt over medium heat. Swirl and cook over medium heat until the butter turns golden brown and smells sweet and nutty. Turn off the heat.
Pour the prepared milk and the browned butter into the bowl with the dry ingredients. Stir until it is thoroughly combined and no dry flour remains on the bottom of the bowl. The dough will be wet and sticky. Turn it out onto a well floured surface and knead only a few times (5-10 turns) until it is a cohesive ball. Do not over knead.
Divide the dough into two pieces and shape each into a ball. Place the balls on a baking sheet covered with foil or parchment. Brush a lightly beaten egg white over the top of each and sprinkle with more black pepper (optional). Cut an “X” into the top of each with a sharp knife, place in the oven, and bake for 45 minutes. Allow to cool before breaking the bread open.