Place cereal mix in the bowl of your stand mixer or a large bowl. Pour boiling water on top. Let the mixture cool until a digital thermometer reads about 110°F (43°C), about 20 minutes.
Mix the yeast, sugar, and all of the warm water/cereal mixture in the bowl of your stand mixer fitted with a dough hook. Cover and set aside.
Mix the salt and flour together. Add the butter to the mixer and eat on low speed for 30 seconds with about a cup of the flour/salt. Scrape down the sides of the bowl and then add the rest of the flour. Beat on medium speed for 5 minutes. Add the seeds/nuts/dried fruit (if using) and beat on medium speed until the dough comes together and pulls away from the sides of the bowl, about 2 to 3 more minutes.
Keep the dough in the mixer and beat for an additional 3-5 minutes, or knead by hand on a lightly floured surface for 5 or 6 minutes. Knead until the dough passes the windowpane test.
Lightly grease a large bowl with olive oil or nonstick spray (I like a wooden bread proofing bowl to maintain temperature). Place the dough in the bowl, turning it to coat all sides in the oil. Cover and allow the dough to rise for 1 ½ to 2 hours or until double in size.
Grease a 9×5-inch loaf pan.
When the dough is ready, punch it down to release the air. Lightly flour a work surface. Roll the dough out into a large rectangle, about 8×15 inches. Roll it up into an 8 inch log and place it in the prepared loaf pan.
Cover the shaped loaf with plastic wrap or a clean kitchen towel. Allow to rise until it’s about 1-2 inches above the top of the loaf pan, about 1 hour.
Preheat oven to 350°F (177°C). Bake the bread towards the bottom of the oven so the top doesn’t burn.
Bake for 35-40 minutes. The bread is done when an instant read thermometer reads the center of the loaf as 195°F-200°F (90°C-93°C) or when you tap the loaf lightly and it sounds hollow.
Remove the bread from the oven and allow to cool before slicing and serving.
Cover leftover bread tightly and store at room temperature for 2-3 days.