Algerian dersa is a spicy garlic and chilli paste, similar to harissa, made by blending garlic, chilli, cumin and paprika together using a mortar and pestle. It is used a lot in the Maghreb region as a seasoning for fish, meat or potatoes. Not everyone uses exactly the same proportions or the same spices. Some people add lemon juice, others add parsley. In short, there are as many variations as there are tastes, but the basic ingredients are almost always the same: garlic, cumin, chilli or cayenne pepper and olive oil.