This recipe works best in a large oval 6-8 quart slow cooker. Roll the pizza dough out onto a large piece of parchment paper. Make sure to roll and stretch to dough into an oval 2 inches longer and 2 inches wider than the crock of the slow cooker. Sprinkle with cornmeal and press into both sides of the crust. Then use the edges of the paper to lower the crust into the crock.
Place the butter and onions in a saute pan. Saute for 1-2 minutes, then add the garlic and saute another 2 minutes. Add the crushed tomatoes, Italian Seasoning, sugar and salt. Simmer for 5 minutes, then remove from heat.
Meanwhile, cook the pork sausage in a separate skillet, breaking apart with a wooden spoon.
Spread the cheese over the bottom of the pizza crust. Lift and stretch the sides of the dough so they stand up past the cheese. Sprinkle the crumbled sausage over the cheese. Then spread the tomato sauce over the sausage. Lift and stretch the sides of the crust again so it is above the edge of the sauce.
Cover the slow cooker with a long piece of paper towel. Then place the lid over the paper towel and pull it tight. This helps catch excess moisture.
Slow cook the pizza for 2-4 hours on high, or 4-6 hours on low. When you are ready to serve, lift the pizza out of the crock by the edges of the parchment paper and sprinkle the top with parmesan cheese and parsley. Cut into 4 pieces.
NOTES: As seen in the images you can make pepperoni deep dish pizzas, or any kind you like! Spread pizza sauce over the bottom of the crust and top with cheese and additional toppings.