Add onions to the stockpot (with the grease), and sauté for 5 minutes, stirring occasionally. Add garlic, and sauté for 1 minute, stirring occasionally. Add the potatoes, chicken stock, and cooked sausage, and continue cooking until the mixture reaches a simmer. Reduce heat to medium-low, and simmer for 10 minutes, or until the potatoes are tender. Stir in the kale and cream, and simmer for an additional 5 minutes. Season with salt and pepper to taste.