You can use any number of dried red chilies for this recipe: Chinese red chili peppers, cayenne peppers, or even Mexican chiles de árbol. For a hotter harissa, leave some or all of the seeds intact.
Place the chilies in a heatproof bowl and pour the water over them. Let soak for 1 hour. Drain the chilies, reserving the soaking liquid.
Seed and devein the chilies. (It’s a good idea to wear rubber or plastic gloves when handling chilies.)
Combine the chilies, garlic, salt, cumin, and pepper in a blender and puree to a smooth paste