01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper or lightly oil it.
02 - In a food processor, pulse pistachios, breadcrumbs, parsley, lemon zest, salt, and pepper until the mixture resembles coarse crumbs. Drizzle in olive oil and pulse once more to combine.
03 - Place salmon fillets on the prepared baking sheet. Brush the tops with Dijon mustard.
04 - Press the pistachio mixture evenly onto the mustard-coated side of each fillet to form a crust.
05 - Bake for 12–15 minutes, or until the salmon is just cooked through and the crust is golden.
06 - Meanwhile, bring a pot of salted water to a boil. Add peas and cook for 2–3 minutes (fresh) or 3–4 minutes (frozen) until tender and bright green. Drain well.
07 - In a food processor or with a potato masher, blend peas, butter, cream, mint, lemon juice, salt, and pepper until mostly smooth but still slightly chunky.
08 - Taste and adjust seasoning as needed.
09 - To serve, spoon the spring pea mash onto plates, top with pistachio-crusted salmon, and garnish with lemon wedges, extra pistachios, and fresh herbs as desired.