Preheat the oven to 200 C, 400 F, Gas Mark 6. Place the basil, garlic, walnuts and 6 tablespoons of olive oil into a food processor and blend until a paste is formed. Transfer to a bowl and stir in the cheese. Cover and refrigerate. Meanwhile, heat the remaining tablespoon of olive oil in a heavy based frying pan. Wash the skate wings and pat dry. Season the flour with salt and freshly ground black pepper and lightly coat the skate wings on both sides, shaking off any excess. Seal the skate quickly in the frying pan, approximately 1-2 minutes each side, then transfer to a baking tray. Spread the pesto evenly over the skate wings and bake in the oven for 15-20 minutes, until the flesh is firm and no longer translucent. Toss the capers in the hot frying pan until crispy and leave to one side. Serve the skate sprinkled with the crispy capers.