Season the salmon pieces with salt and pepper. Place a large frying pan over medium–high heat. Add half the olive oil and let it get nice and hot. Add the salmon pieces and cook for about 5 minutes each side (or however you like it). Remove the salmon and set aside.
Melt the butter and add the remaining olive oil to the pan. Add the onion and cook, stirring, for 1–2 minutes. Then add the garlic and do the same. Add the chicken stock (it should bubble) and stir for 2–3 minutes. The liquid should reduce and thicken over this time (if it doesn't, increase the heat). Stir through the sun-dried tomatoes.
Reduce the heat to low and pour in the cream. Simmer for about 5 minutes. Season well, then stir through the spinach and peas. Add the grated parmesan and combine.
Return the salmon pieces to the pan and nestle them into the sauce. Scatter over the parsley and squeeze over some lemon juice.