Heat a large, heavy bottom pot on the stove over high heat. Add in the olive oil. When the oil shimmers, add in the sausage. Allow to brown, breaking it up with a spatula as it cooks, for 5-7 minutes. When the sausage is broken up and browned, add in the carrots, onion, celery and shallot. Allow to sweat for 5-6 minutes. Then add in the garlic and red pepper flakes. Cook an additional 2 minutes, stirring frequently. Add in the tomatoes and cook until the juice has been absorbed. Add the chicken stock. Bring the soup to a boil. While the soup is boiling, skim the fat off the top with a ladle. It will pool in the middle of the soup. Once skimmed (to the best of your ability!) reduce the heat to low and simmer for 20 minutes. After 20 minutes have passed, add in the kale. Simmer for another 15 minutes, stirring occasionally. Taste and adjust seasonings. Serve hot and happy eating!