Preheat Oven: Preheat your oven to 400°F (200°C). Lightly oil a 9x13 inch casserole dish and set aside.
Sauté Aromatics: Heat the olive oil in a large skillet over medium high heat. Add the chopped onion and garlic. Cook for 2-3 minutes, until fragrant and the onion is softened.
Make the Roux: Sprinkle the flour over the onions and garlic. Stir constantly for about 1 minute to cook the flour.
Add Liquids: Slowly pour in the vegetable broth while whisking continuously to prevent lumps. Then, slowly whisk in the almond milk. Continue whisking until the mixture is smooth.
Thicken the Sauce: Bring the mixture to a boil, stirring often. It will begin to thicken after a minute or two.
Add Vegetables and Chickpeas: Stir in the frozen mixed vegetables, chopped potato, and drained chickpeas. Reduce the heat and let the filling simmer for 5-10 minutes, stirring occasionally, until the sauce thickens further and the potato begins to soften. Stir in the salt.
Initial Bake: Pour the filling into the prepared casserole dish. Place it in the oven and bake for 15 minutes while you prepare the biscuit dough.
Make Biscuit Dough: In a large bowl, whisk together the flour, baking powder, and salt. Make a well in the center. Pour in the melted vegan butter and almond milk. Stir with a spoon until just combined; do not overmix. Gently fold in the vegan cheddar shreds, if using.
Top the Filling: After 15 minutes, carefully remove the casserole dish from the oven. Drop large spoonfuls (about ¼ cup each) of the biscuit dough evenly over the hot filling.
Final Bake: Return the dish to the oven and bake for another 20-25 minutes, until the biscuits are golden brown and cooked through, and the filling is bubbly.
Rest and Serve: Let the pot pie cool for about 10 minutes before serving. Garnish with fresh parsley, if desired.