Preheat the oven to 180°C (fan) and line a baking tray with baking paper. Wash the sweet potatoes thoroughly, then pierce them several times with a knife to allow steam to escape. Place the sweet potatoes on the prepared tray and bake for about 40 minutes, or until they are soft when pierced with a fork.

While the sweet potatoes are finishing baking (about 10 minutes left), heat a dash of water or a bit of olive oil in a frypan over medium heat. Add the chopped onion, sliced mushrooms, and minced garlic to the pan. Sauté them until the mushrooms release their juices and turn golden, and the onions are soft and fragrant.

Reduce the heat to low and stir in the spinach leaves, tahini, nutritional yeast flakes, salt, and black pepper. Cook everything together, stirring occasionally, until the spinach wilts and the mixture becomes creamy. I find that adding the tahini at this stage gives the filling a rich, smooth texture.

Add the juice from half a small lemon to the pan along with a dash of cayenne pepper if you want some heat. Stir everything well to mix the flavors together. I like to squeeze the lemon directly into the pan for maximum freshness.

Remove the sweet potatoes from the oven and let them cool slightly. Slice each potato lengthwise and gently fluff the insides with a fork to create space for the filling. Spoon the creamy mushroom and spinach mixture from Steps 2–4 into the sweet potatoes, filling them generously.