Bring a pan of salted water to a boil and cook the potatoes until tender. Drain, and mash with 3 tbsp sour cream, seasoning to taste.
In the meantime, heat a little olive oil in a pan over medium heat. Add the garlic, lemon zest and peas and cook for about 3-4 minutes.
Add the white wine and cook for about 2-3 minutes until the alcohol has burned off.
Add the remaining sour cream and cook for 1-2 minutes until melted. Add the parsley, season to taste with salt, pepper, and lemon juice, and blend until smooth.
Season the flour with salt and pepper and dredge the salmon fillets through it.
Heat some olive oil in a non-stick pan over medium-high heat. Add the salmon and fry for about 2 minutes on each side, or until cooked to your liking.
Serve the salmon hot with the mashed potatoes and the green sauce.