Bratwurst and Beer Soup

Heat the oil in a 6-quart pot over medium-high heat for 1 minute. Add the bratwurst and sauté until lightly browned. Transfer to a bowl. Combine the stock, leeks, potato, and pepper in the same 6-quart pot. Cover and bring to a boil. Reduce the heat and simmer until the potatoes are tender, about 15 minutes. Transfer half the mixture to a bowl. Using a potato masher, mash the vegetables remaining in the pot. Stir in the bratwurst and reserved vegetables. Stir in the bell pepper and beer and simmer 5 minutes. Taste and season with salt if needed. Top each serving with the chives.