1. In the bowl of a stand mixer, combine milk, sourdough starter, butter, sugar and eggs.  Mix well using the dough hook attachment.

2. Add salt, flour, baking soda and baking powder.  Mix for 5-7 minutes.  You can do the windowpane test by slowly stretching the dough upwards to see if it stays together and if you can see through it similar to a window.

3. Wrap ball of dough in plastic wrap or place in an airtight bowl and allow to ferment at room temperature overnight, or in the refrigerator for up to a week.

4. When you’re ready to bake the sourdough stromboli, preheat the oven to 350 degrees.

5. Brown sausage or hamburger if using any.

6. Roll dough into approximately a 16-inch rectangle on parchment paper (see video below).

7. Place meats/cheeses, mushrooms, mustard, sausage etc. down the center of dough.

8. Fold each side of the dough over the top of the meat/cheese mixture and seal the edges.

9. Transfer dough using parchment paper onto a baking sheet or use a pizza peel and transfer to a preheated pizza stone.  

10. In a small bowl, beat one egg and coat the top of the dough with the egg wash using a pastry brush.

11. Bake at 350 degrees for 25 minutes or until a light golden brown.

12. Slice using a pizza cutter or sharp knife.

13. Serve with marinara sauce for dipping and a side salad for a delicious and healthy meal.

14. Once cool, the slices can be placed into freezer bags or an airtight container and frozen for up to three months.