Prick all the potatoes with a fork.
Drizzle each potato with a little bit of olive oil.
Rub the oil and salt evenly until all potatoes are coated.
Wrap each potato tightly in aluminum foil paper.
Place them in your slow cooker (6 quart or larger).
Cover and cook on High heat for about 4 hours on or Low heat for about 8 hours.
When the potatoes are done, remove from crockpot and unwrap the foil carefully.
Use a sharp knife to cut in half lengthwise.
Use a spoon to remove the pulp. Be sure to leave some of the pulp intact in the skin so that the potatoes hold their shape and don't fall apart, when stuffed later.
Add this potato pulp in large mixing bowl, along with milk, sour cream, Italian seasoning, salt, pepper, 1 tbsp cheddar cheese, 1 tbsp mozzarella cheese.
Use a potato masher to mash everything until smooth.
Heat in the microwave for 1 minute and mash/ mix again to make the mixture even smother.
Add spoonfuls of this mixture into the potato skins.
Sprinkle remaining cheddar cheese and mozzarella cheese on top of potato skins.
Place these stuffed potatoes back in the crockpot.
Cover and cook on High heat for about 20 minutes or until cheese is fully melted.
Garnish with fresh herbs. I also sprinkled some black pepper on top.
Serve immediately and enjoy!