Slice sausage lengthwise then cut into 5mm slices.
Heat oil in a large pot over medium-high heat. Brown sausage about 5 minutes. Stir in onion; cook 5 minutes. Stir in chickpeas and juices, tomato sauce and sherry. Season with oregano, chilli flakes, black pepper, garlic powder and seasoning.
Simmer, stirring occasionally, at least 10 minutes (1 hour or more is preferable).