Pat the shrimp and scallops dry with kitchen paper and season with salt and pepper.
Heat the olive oil in a large pan. Add the scallops flat side down and cook without moving until golden brown on one side. Turn the scallops over and cook for a further 1-2 minutes. Transfer to a bowl.
Add the shrimp and pan fry for a couple of minutes minutes until the shrimp just turn pink. Set aside with the scallops.
Add the butter and melt over medium heat. Sauté the shallots for five minutes and then add the sun-dried tomatoes and garlic. Stir in the lemon juice and cook for a further two minutes then lower the heat.
Stir in the cream and bring to a low simmer. Add the shrimp and scallops back to the pan.
Add the chopped spinach, stirring it in until it wilts. Stir in the grated Parmesan, if using.
Tear the basil leaves and stir into the sauce. Taste and season with salt and pepper as needed. Sprinkle with the lemon zest and serve.
If the sauce seems really thick you can add a little chicken stock or dry white wine.