Bring a large pot of salted water to a boil. Add the pasta and cook it according to the package directions. Drain the pasta into a colander when done.

Place the cashews and water into a blender and blend until smooth. Set aside.

Coat the bottom of a large skillet with two tablespoons of the vegan butter and place it over medium heat.

When the butter has melted, add the mushroom slices in a relatively even layer. (Note 2)

Cook the mushrooms for about 5 minutes on each side, until golden brown. Remove them from the skillet and transfer them to a plate when done.

Add the remaining tablespoon of butter to the skillet. Once the butter melts, add the onion, celery, and carrots.

Cook the veggies for about 5 minutes, stirring frequently, until they begin to soften.

Add the garlic and flour. Stir the mixture well to coat the vegetables with flour and continue cooking the mixture for about 1 minute.

Slowly begin adding the non-dairy milk, stirring in just a bit at a time to prevent the flour from clumping. Once all of the milk has been added, stir in the cashew mixture, bouillon, thyme, and cooked mushrooms.

Raise the heat and bring the mixture to a low boil. Lower the heat and let it simmer for about 10 minutes, stirring frequently, until thickened slightly. Preheat the oven to 350°F while the sauce simmers.

Remove the skillet from heat and stir in the lemon juice.

Combine the cooked pasta, sauce mixture and peas in a 2-quart casserole dish. (Note 3)

Season the mixture with salt and pepper to taste.

Cover the casserole dish and place it into the oven. Bake the casserole for about 20 minutes, until heated throughout.

Remove the foil from the dish and sprinkle the casserole with panko breadcrumbs. Bake 5 minutes more.

Let the casserole sit out for 5 minutes before serving.