Mash the butter in a small bowl. Finely chop half the basil leaves and mix them into the butter with plenty of seasoning and set aside.
Heat a little drizzle of oil in a frying pan over a medium–high heat. Add the salmon, skin-side down, and fry for 5–6 minutes until golden and crisp. Turn over and cook for just a minute or 2 more, then add the basil butter and let it melt and foam around the salmon; spoon it over the top of the fillets.
Add the chopped walnuts and cook for a further minute or so.
Meanwhile, mix the tomatoes and fennel in a large bowl with the garlic, vinegar and remaining basil leaves. Season well and add a good glug of extra-virgin olive oil.
Serve the buttery salmon with the salad.
Notes
A seriously light and fresh supper. This is a perfect example of using simple good-quality ingredients and letting them do all the work.