Place a large saucepan over medium heat and add in 1 tbsp of the olive oil. Once oil heats, add in the garlic and cook for 30 seconds. Add in mushrooms and cook until mushrooms have browned, seasoning generously with salt and pepper. Once done, turn off the heat and leave the skillet (with veggies) on the stove.
Place a medium saucepan over medium heat and add in the vegan butter. Once melting, add in the whole wheat flour. Whisk to thicken and then add in your chicken broth, bring to a boil and lower heat to a simmer. Simmer for about 2 minutes or until reduced and whisk the mixture as it begins to thicken.
Once the gravy is thick, add back in the mushrooms (with garlic), season with pepper and mix to combine thoroughly. Set aside in a gravy bowl.
In the saucepan with the mushrooms, add in the other 1/2 tbsp of the olive oil and turn heat to medium. Once the oil heats, add in the leeks and cook for 2 minutes. Then, add in the zucchini noodles, season with garlic powder and more pepper, and cook for 2 minutes, tossing frequently, or until zucchini has softened.
Plate the zucchini noodles into a serving dish and place gravy bowl aside it, along with serving tongs.