Place the mussels in a large bowl of cold water. Use a small knife to remove any barnacles and pull away the beard. Discard any mussels that are damaged or won’t close when tapped.
To cook the mussels: Place the wine in a large saucepan over a high heat. Add the cleaned mussels and cover tightly with a lid. Allow the mussels to cook for 3-4 minutes, shaking the pan from time to time to ensure they cook evenly.
Discard any that have not opened.
Remove the mussels from the cooking liquid and allow to cool. Keep the cooking liquid to include in the sauce. When the mussels are cool enough to handle remove the mussel meat from the shells and set aside. Discard the shells.
To make the sauce: Heat a little oil in a saucepan over a low heat. Add the shallots and garlic and sauté gently for about 5 minutes, do not let them brown.
Add the mussels, red pepper, squeeze of lemon juice and reserved cooking liquid and gently warm through, taste and season with some black pepper. As the mussels are naturally salty you shouldn’t need any salt.
To cook the salmon: Meanwhile heat a little more oil in a non-stick frying pan big enough to take the salmon. Add the salmon into the pan and cook for 2 minutes, turn the heat down to medium, turn and cook the salmon for 2 minutes on the other side.
At the last minute add the spinach to the sauce and heat gently for a minute or two to allow the spinach to wilt.
Serve the salmon with the mussel sauce spooned over. Steamed baby potatoes would be delicious with this dish.