Photograph: Martin Poole
Rinse the mussels in a colander under cold running water, pulling out any beards (hairy strands) from the shells using a small sharp knife.
Melt the butter and oil in a large pan. Add the shallots, garlic and chorizo; cook over a low heat until the shallots have softened. Stir in the chopped almonds and most of the parsley.
Tip in the sherry and mussels; turn the heat to high. Cover tightly with a lid and cook for about 5 minutes, shaking the pan occasionally. Discard any mussels that refuse to open.
Spoon into large, deep bowls and scatter with the rest of the parsley. Eat with crusty bread and pop a dish in the centre of the table for everyone to put their empty shells in.