In a pan, heat the oil over medium and add the onions. Saute until they are translucent.
Add in the sausage and break apart while cooking.
When the sausage is almost done, add in the garlic, red pepper flakes, cayenne, paprika, basil, oregano, black pepper and salt. Continue cooking until the sausage is cooked through, and drain off any grease that accumulates in the pan.
While the onions and sausage are cooking, place the chicken stock, potatoes and celery into a Dutch oven and bring to a slow boil. Turn the heat to medium, and let the vegetables simmer for about 20 minutes or until the potatoes are fork tender.
Add the sausage to the Dutch oven, along with the milk and cheese. Stir to combine. Serve once all ingredients are warmed through.