In a medium bowl, whisk together 6 eggs, 2 tbsp sour cream and salt & pepper to taste. Add strips of ham to the egg mixture and set aside.
Heat a large skillet over medium heat and add 1 tbsp of oil. Saute sliced mushrooms until golden (about 5 minutes), seasoning lightly with salt and pepper. Remove the mushrooms from the pan and set aside.
In the same skillet, melt 1 tbsp of butter over medium heat. Add the eggs and ham mixture, stirring and scrambling until the eggs are just cooked through (about 3 minutes). Be careful not to overcook. Remove from the pan and set aside.
Spread 1 tbsp of sour cream in the center of a tortilla. Top with 1/4 of the cooked eggs, shredded mozzarella cheese and sauted mushrooms. Optionally, add 1-2 tbsp of diced tomatoes, but skip the freezing the burritos.
Fold the top flap over the filling, then fold the edges tightly and roll to seal with the bottom flap. Repeat with the remaining burritos.
Heat a large skillet over heat with 2 tbsp of oil. Place fresh or thawed burritos in the hot pan, folded side down and cook until golden brown on all sides (about 2 minutes per side), adding more oil as needed.
Omit the tomatoes if planning to freeze the breakfast burritos.
You can use 8 inch medium size tortillas, but they may be a bit more challenging to wrap and should not be filled as full.
