Melt 25 g (1 oz) butter and cook the fennel in it for 30 seconds. Blend in the flour and cook for 1 minute, stirring well. Work in the milk and simmer until the sauce is creamy and smooth. Season to taste with salt and pepper and stir in the remaining butter. Serve with grilled mackerel and other fish.
This recipe comes from Mary Norwak and I have found it to be an exciting accompaniment, especially to dull white fish.