Place cereal mix in a medium heat-safe bowl. Pour boiling water over top and gently stir. Let stand at room temperature until mixture reaches 110F, about 30 minutes.
Place warm milk in the bowl of a stand mixer fitted with a dough hook OR a large bowl. Dissolve yeast in milk and let stand 5 minutes until foamy.
Mix cooled cereal-water mixture, vegetable oil, honey, and egg into yeast mixture until smooth. Add salt, sunflower seeds, chia seeds, whole wheat flour, and all-purpose flour to bowl and mix on low speed OR with a wooden spoon if making dough by hand until dough pulls away from sides of bowl, about 2 minutes of mixing (dough will be smooth and ball-shaped)
If making dough in stand mixer, knead dough in mixer on low speed 5-7 minutes until dough is stretchy and elastic. If making dough by hand, turn dough onto a lightly floured surface and knead by hand until dough is stretchy and elastic, about 10 minutes of kneading.
Place dough in a greased bowl, turning once to grease top. Cover bowl with plastic wrap and let rise in a warm place at room temperature 1 to 1-1/2 hours until dough is doubled in size.
Once dough has doubled in size, preheat oven to 375F. Line two 9×5 loaf pans with parchment paper OR lightly grease. Set aside.
Punch risen dough down and turn onto a floured surface. Divide dough in half and roll each half out into a 9×12 inch rectangle. Tightly roll each rectangle starting at the short side, pinching ends to seal. Transfer each loaf to prepared pans, tucking ends under.
Brush each loaf with egg white/water mixture and sprinkle with oats. Cover pans with plastic wrap and allow loaves to rise in a warm place at room temperature 30-45 minutes until doubled in size.
Bake loaves at 375F 20-25 minutes until bread is a deep golden brown and registers 190F on a kitchen thermometer.
Cool bread completely in pans on a wire cooling rack. Once cooled, remove from pans and use a serrated knife to cut into slices. Enjoy!