Melt the vegan butter in a large skillet and pan fry the sliced leeks. Sprinkle with a bit of salt and cook until the leeks are softened.
Add the grated garlic and cook for another minute, then add the sage, miso paste and nutritional yeast.
Drain the beans, keeping the water from the tin, and add them to the skillet. Stir to mix, then pour in the aquafaba and mash part of the beans in the skillet using a potato masher.
Pour in the vegetable stock and stir to mix evenly. Simmer on low heat for 10 minutes or until the beans are creamy. Season to taste with salt and pepper.
Remove the skillet from the heat and sprinkle the top with vegan cheese. Place the skillet under the grill of your oven to melt the cheese and give it a delicious melty crust on top.
In the meantime, fry a few fresh sage leaves in olive oil over medium heat until crispy.
Serve the creamy bean skillet with the crispy sage leaves on top and enjoy alongside potatoes or with freshly toasted bread.