Around 8:30pm: In the bowl of a stand mixer, add starter, honey, milk, and water. Whisk with fork to combine. Then add whole wheat flour, bread flour, and ap flour. Attach dough hook and mix on speed 3 of a Kitchenaid until no dry bits appear, about 30 seconds. Let dough rest for 45 minutes, with cloth covering the mixer.

Add salt and turn mixer on low, speed 2 of Kitchenaid. Add a chunk of butter and once you can no longer see it, add the next, until all butter is in dough. Then turn to speed 4 on Kitchenaid mixer (medium) and mix for 7 minutes. Remove bowl from the mixer, cover with a plastic bag, and let rise overnight in a cool spot, between 65-68 degrees F.

Around 7:30am, your dough should have increased in size by about 50%. It will have rounded edges and have puffed up, but still look a bit dense. It will not have bubbles or big jiggly like regular sourdough. Dust your countertop with flour and place dough onto it, and let rest for 10 minutes.

Gently press it into a square-ish shape, popping any bubbles you may see coming through surface. Fold one of the sides inwards about 1/3 of total length of dough. Then begin rolling that side up, until the loaf resembles a log. Use your hands to tuck ends of log in, and gently pull the log towards you to create a bit of tension and seal the seam.

Use a bench scraper to pick the dough up and place seam-side down in a greased 9 x 5 inch loaf pan. Allow the dough to rest in a warm spot, covered with a plastic bag (that does not touch the top of pan/dough) until the dough has risen to the rim or just above the pan, about 3 to 4 hours. When finished proofing, brush dough with water and sprinkle with oats, if desired.

Preheat oven to 400 degrees F, with a pan of water that has 2 cups of water in it, placing pan on bottom rack of oven (this creates a steamy environment that the bread loves). Bake bread for 15 minutes, then remove the pan of water. Continue baking for another 15-20 minutes, until bread is golden brown on top. To check for doneness, insert thermometer into center of bread, which should read at least 205 degrees F when complete. While warm, brush top of loaf with a tablespoon or two of butter to keep it soft.

Let cool in pan for about 10 minutes, then using oven mitts gently tip the bread out. Let finish cooling until completely cool, at least 1 1/2 hours before slicing. Slicing too early while it is warm will result in gummy bread.