Preheat oven to 400°F.
Melt vegan butter in a skillet over medium heat. (I like to cook everything in a large cast iron skillet so that I can transfer it straight to the oven to bake.)
Sauté onions, celery and carrot for 3-5 minutes, or until onions are translucent. Add garlic and sauté for 1 more minute.
Sprinkle vegetables with all-purpose flour and stir to coat. Cook for 1-2 minutes, stirring constantly.
Optionally, deglaze the pan with a splash (about 1/3 cup) dry white wine. Stir and reduce until most of the liquid is gone — this should take just a minute or two.
Pour in vegetable broth and stir to dissolve the flour. Scrape up anything that might be sticking to the bottom of the pan.
Add in the homemade cashew cream (or plant milk) and poultry seasoning (or fresh herbs). Stir to combine.
Stir in the chopped vegan chicken and peas.
Allow the filling to come up to a simmer. Reduce heat to low and allow it to simmer until thickened.It will thicken quickly if using homemade cashew cream. Store-bought plant milk tends to have less thickening power, so it may require a few extra minutes. Let it simmer until the filling is as thick and creamy as you like.If you prefer a slightly thinner consistency, feel free to add in an extra splash of broth. This is a good time to taste the filling and add salt and pepper to preference. How much salt is needed will depend on the brand of vegetable broth you're using.