Season the salmon fillets with salt and pepper, and put a medium Saucepan on high heat. When hot add the 2 tablespoons of the olive oil, reduce the heat to low-medium, and add the salmon fillets. Sear for 4 minutes until the salmon has a nice golden colour then flip and sear for 2-3 more minutes.
In the meantime, put a medium pot on high heat and bring to a boil. Add your peas, 2 tablespoons of the mint leaves and simmer according to package instructions, usually 7-8 minutes.
Strain the peas and place in a high-speed blender with the metal blade on. Add the remaining 2 tablespoons of mint leaves, 70 ml from the water that the peas were boiling in, the ½ lemon Zest, any cheese or butter if using, add the salt and pepper and blend until smooth. If too thick add more water. Keep aside.
In another small saucepan on high heat drizzle the 2 tablespoons of the olive oil and a minute later add the onions. Reduce the heat to medium and sauté for about 2 minutes until you obtain a nice light golden colour. Deglaze with the wine and let the alcohol evaporate and the liquid to reduce to half. Add the lemon juice and zest and simmer for 3-4 minutes until further reduced and a minute before taking off the heat season with salt and pepper and add the mint.
To serve add in the centre of a plate the pea puree and on top the salmon. Drizzle with the sauce and garnish with couple of mint leaves.