Gather your ingredients so that you have everything close at hand on the counter or table.
In a small saucepan, heat the whole milk with butter until the butter begins to melt. Remove from heat.
In a large mixing bowl with an attached dough hook, combine 3 cups of all-purpose flour, onion soup mix, granulated sugar, instant yeast, and kosher salt.
Add in the lukewarm milk mixture. Stir in the large beaten egg until combined.
Turn out onto a floured surface and add the remaining flour. Knead until smooth and silky, 5-7 minutes.
Place in a greased bowl. Cover and allow to rise until double, approximately 60-90 minutes.
Preheat oven with baking stone to 350 degrees. Punch down dough. Cut into two pieces and form into mounds. Place on parchment paper. Cover with cotton dish towel and allow to rise for 30-40 minutes until double.
Prepare Egg Wash and Topping
In a small bowl, mix together the egg and water to make an egg wash.
Brush each loaf with the beaten egg wash and sprinkle with sesame seeds.
Using a pizza peel, transfer each loaf on parchment paper to the baking stone in the preheated oven. Bake for 35-40 minutes until golden brown. Makes 2 rustic loaves.
Notes
*Unless otherwise indicated, all butter used on this recipe site is salted.