Cook the spaghetti as directed on the package. Reserve a 1/2 cup of the pasta water before draining.
Place the peas in a microwave safe bowl and cover with water. Cook till heated through but not mushy. Reserve 2 tbsp of cooked peas to use as a garnish at the end.
In a food processor add the peas, walnuts, garlic, miso, lemon zest, juice and salt. Pulse until you get a rough paste, then add the oil one tablespoon at a time and pulse until smooth.
Transfer pasta and pesto to a bowl and toss to combine. If the pesto is too thick add the reserved pasta water to thin out, 1 tbsp at a time.
Serve garnished with the 2 tablespoons of reserved peas, radishes, and a sprinkle of black pepper. Enjoy!