Peel the sweet potatoes and slice them thinly.
Cut the onion and broccoli into bite-sized pieces.
Heat olive oil in a pan and sauté the onion and broccoli.
Lay the sliced sweet potatoes in a gratin dish.
Place the sautéed vegetables on top of the sweet potatoes.
Mix soy milk with salt and pour over the vegetables.
Sprinkle vegan cheese on top.
Bake in the oven at 200°C for 15 minutes.