Preheat the oven to 425°F. Poke holes in the sweet potatoes and spray with cooking spray or cover with olive oil (or oil of choice). Sprinkle each with salt. Roast in the preheated oven for 1 hour, until fork-tender.
4 large sweet potatoes, 1 Tablespoon olive oil, Kosher salt to taste
Add all of the cubed butter to a medium saucepan over medium heat. Cook and stir for 4-5 minutes until it bubbles and froths, and you start to see small brown bits form on the bottom of the pan. Optionally, add the sage leaves in the last 1-2 minutes of cooking to crisp slightly. Remove it from the heat and remove the sage leaves, reserving them for garnish.
3/4 cup unsalted butter, 8-10 sage leaves
When the potatoes are done, cut a slit down the center to allow them to cool quicker. Turn the oven temperature down to 350°F and spray a 9x13-inch (or 3qt) casserole dish with nonstick spray.
When they’re cool enough to handle, peel away the skin from the flesh or scoop it out with a spoon. Add the sweet potatoes to a mixing bowl and mash well with a potato masher. For really smooth filling, use an electric mixer to blend it well.
Add 4 Tablespoons of the brown butter, making sure you get some of the brown bits that settle at the bottom of the pan. Add 1/2 cup of the brown sugar, eggs, cinnamon, vanilla, and a pinch of kosher salt. Taste the filling with a spoon and add more salt as needed.
1 1/2 cups light brown sugar, 2 large egg, 1 teaspoon cinnamon, 1 teaspoon vanilla extract
To a separate medium mixing bowl, add the remaining brown butter, brown sugar, flour, pecans, and salt and stir to combine.
1/2 cup all-purpose flour, 1 1/2 cups raw pecans
Transfer the sweet potato filling to the prepared casserole dish. Sprinkle the topping evenly over top. Bake for 35-40 minutes, until the sides are bubbling and the pecans are golden brown. Cover with foil if the nuts are browning too quickly. Serve warm with crispy sage or flaky sea salt.