Place cereal mix in he bowl of a stand mixer fitted with a dough hook attachment and add the boiling water, stirring to combine. Let stand for 1 hour, stirring occasionally, until cooled to 100-105 degrees F.

Add honey, butter, and yeast to the cereal mixture and stir to combine. Let sit for 5 to 10 minutes. Stir in the salt.

Add both the bread and whole wheat flours, 1 cup at a time, along with any additional seeds or nuts with the last cup of flour. Knead just until the dough starts to come together in a ball. Cover with plastic wrap and let sit for 20 minutes.

Remove plastic wrap and knead for 3-4 minutes until the dough starts to come away from the sides of the bowl. If the dough is not clearing the sides of the bowl, continue to add 2 tablespoons of additional all-purpose flour until it does. Knead another 5 minutes on medium speed.

Shape into a ball and transfer to a lightly greased bowl. Cover with plastic wrap and let rise for 1 hour until doubled in size.

Prepare two 9x5-inch loaf pans by lightly greasing them with cooking spray or oil.

Divide dough in half and pat one half into a 9x6-inch rectangle on a lightly floured surface. Roll the dough up into a cylinder, then place seam-side down in one of the loaf pans. Repeat with the other half of the dough.

Spray the loaves with cooking spray, then sprinkle with extra multigrain cereal or oats. Cover loosely with plastic wrap and let rise at room temperature until nearly doubled in size, around 30-45 minutes.

Preheat oven to 375 degrees F.

Bake the loaves for 35-40 minutes until browned on top. You can test the inside of the loaves with a digital thermometer to see if it registers 195 to 200 degrees F in the middle to know if the bread is done.

Cool the loaves in the bread pans for 5 minutes before removing and cooling completely on a wire rack.