Stir-fry the pepper in the oil for 2 minutes. Add the shallots and go on stir-frying for 3 more minutes. Then add the other ingredients and simmer, uncovered, for 45 minutes. By this time the sauce will be quite thick. Stir, adjust the seasoning, and the basic sauce is ready to serve. It can be made some hours in advance and reheated.
To make a smooth sauce, pass it through a fine sieve