Prepare the Sweet Potatoes:
Preheat your oven to 375°F (190°C) and lightly grease a casserole dish.
Place the sweet potato cubes in a large pot, cover with water, and bring to a boil. Cook until tender, about 15-20 minutes. Drain and let cool slightly.
Make the Filling:
In a large mixing bowl, mash the cooked sweet potatoes until smooth.
Stir in the plant-based milk, maple syrup or brown sugar, vegan butter, vanilla extract, cinnamon, nutmeg, and a pinch of salt. Mix until well combined.
Spread the sweet potato mixture evenly into the prepared casserole dish.
Prepare the Streusel Topping:
In a small bowl, combine the chopped pecans, flour, brown sugar, melted vegan butter, and a pinch of salt. Mix until crumbly.
Assemble the Casserole:
Sprinkle the pecan streusel evenly over the sweet potato mixture.
Bake:
Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and the casserole is heated through.
Serve:
Let the casserole cool for a few minutes before serving. Enjoy this warm, comforting dish as a side or a sweet ending to your meal.