Mix hot water and oats. In a large mixing bowl, combine the hot water and oats. Stir and let it cool to lukewarm, around 90℉ (32℃). Do not skip this step, as hot water can kill the yeast.
Knead the dough. Add the honey, brown sugar, salt, all-purpose flour, whole wheat flour, softened butter, and instant yeast to the bowl. Stir until combined. If the dough seems dry, add water a tablespoon at a time until it comes together. Knead by hand, using a stand mixer, or in a bread machine on the dough cycle until smooth and elastic. The dough should pass the "windowpane test" when stretched. (If using a bread machine, skip to step 4.)
First rise. Transfer the dough to a clean, lightly oiled bowl. Cover with a damp tea towel and place in a warm area to rise until doubled in size, about 1 hour. A slightly warmed oven that is turned off works well for this.
Shape into loaf. Once the dough has doubled, turn it out onto a lightly floured surface. Stretch it to match the length of your loaf pan. Tuck in the corners, then roll it up tightly into a log. Pinch the seams to seal.
Second rise. Place the dough, seam side down, into a lightly oiled loaf pan. Cover with greased plastic wrap and let it rise in a warm place until it reaches about 2 inches above the pan, approximately 45 minutes to 1 hour. Preheat your oven to 350°F (175°C) during the last 15 minutes of this rise.
Bake. Remove the plastic wrap from the risen dough. If desired, brush the top with water and sprinkle oats on top. Bake in a preheated oven at 350°F (175°C) for 35-45 minutes or until golden brown. Cool on a wire rack. Allow the loaf to cool completely before slicing. The bread stays fresh at room temperature for up to 3 days when tightly wrapped or can be frozen for up to a month.