Prepare the Vegetables
Dice celery, slice mushrooms, and rinse white beans. Use frozen vegetables to save time—no need to thaw.
Sauté the Base
Melt butter in a large skillet over medium heat.
Add mushrooms and celery, sauté until softened (5-7 minutes).
Stir in garlic powder, salt, and pepper.
Thicken the Sauce
Sprinkle in flour and cook for 1 minute, stirring constantly.
Gradually whisk in almond milk.
Simmer until the sauce thickens, about 3-5 minutes.
Combine the Filling
Add white beans, frozen vegetables, and pearl onions.
Stir in thyme and balsamic vinegar. Adjust seasoning if needed.
Assemble the Pot Pie
Pour the filling into a pie dish or ramekins.
Lay the prepared pie crust over the filling, trim excess dough, and crimp edges.
Cut small slits in the crust for steam to escape.
Apply Egg Wash
Whisk the egg with a splash of water and brush it over the crust for a golden finish.
Bake
Preheat the oven to 400°F (200°C).
Bake on the center rack for 25-30 minutes, until the crust is golden brown.