Preheat the oven to 400°F (200°C) and line a baking sheet with aluminum foil. Wash and clean the sweet potatoes, then use a sharp knife to cut a slit in each one. Arrange the sweet potatoes on the prepared baking sheet and bake in the oven for 1 to 1.5 hours, or until they are cooked through and soft. Once done, set aside to cool so they are easy to handle.

Reduce the oven temperature to 350°F (175°C). Scoop the flesh out of the cooled sweet potatoes from Step 1 and place it in a deep bowl. Mash the sweet potato with a fork or potato masher to your desired texture. Add 2 tablespoons maple syrup, 1 teaspoon vanilla extract, 1 tablespoon melted butter, 1 1/2 teaspoons ground cinnamon, and 1/4 cup heavy whipping cream. Mix well, tasting the mixture to adjust sweetness if desired. I like to go a bit light on the syrup at first and add more if the potatoes need it, depending on their natural sweetness.

Transfer the sweet potato mixture from Step 2 to a 2-3 quart baking dish and level it with the back of a spoon to create an even surface. Set aside while preparing the crumble topping.

Cut 6 tablespoons of cold butter into small cubes and place them on a plate. In a separate bowl, combine 1/2 cup all-purpose flour, 1/4 cup packed brown sugar, and 1/2 cup chopped pecans. Add the cold butter cubes and mix with your fingers until a crumbly topping forms. Sprinkle this topping evenly over the sweet potato mixture in the baking dish. I like to keep the butter nice and cold—this helps create a crisp, golden finish on the topping.

Bake the assembled casserole in the oven at 350°F (175°C) for 20-25 minutes, or until the top is golden brown and crisp. Remove from the oven and set aside while you prepare the pecan maple sauce.

In a skillet, melt the remaining 2 tablespoons of cold butter over medium heat. Add the remaining 1/2 cup chopped pecans and toast for a couple of minutes, stirring frequently until fragrant. Pour in 1/2 cup maple syrup and mix well. Allow the mixture to boil gently for a couple of minutes, then turn off the heat. For an extra boost of nutty flavor, I sometimes let the pecans get a light golden brown before adding the syrup.

Pour the warm maple pecan sauce from Step 6 evenly over the baked sweet potato casserole. Serve immediately while the dish is hot and the topping is crisp.