Bring a large pot of water to a boil over high heat.
Meanwhile, heat 3 Tablespoons of the olive oil in a large skillet over low heat. When the oil is hot, add the garlic. Cook until the garlic is tender, about 5 minutes. You will know the garlic is ready if you taste it and it is mildly flavored. Be careful not to brown the garlic. Transfer the garlic and oil to a glass bowl.
Add the parsley, lemon juice, white miso, and white wine into your blender, but don’t blend it just yet.
When the water is boiling, add the peas. Cook for 60-90 seconds (this applies to both frozen and fresh peas) until the peas are just (thawed and) tender. Drain the peas immediately, saving the water if you need it to boil the pasta, and rinse the peas in a colander under cold water to stop the cooking. When the peas are cool, transfer 1 ½ cups of the peas to the blender and set the rest of the peas aside.
When the garlic and oil are cool, transfer them into the blender as well. Blend on high until smooth (see note).
You can boil the pasta now, if you haven’t done so already, per the instructions on the package or recipe you’re following, draining it when it becomes al dente.
Heat the remaining 3 Tablespoons of oil over medium heat. When hot, add the mushrooms. Cook and stir until tender and just cooked through, about 5 minutes. Add the pasta, blended sauce, and reserved peas into the skillet. Stir until evenly coated and heated through. Stir a bit of white wine (or vegetable stock) into the sauce if it becomes too thick during this process. Add salt to taste.
Garnish with parsley and lemon juice, as desired, and serve immediately.