• Begin by preparing the browned butter. Heat 8 tablespoons of unsalted butter in a small skillet over medium heat until melted and bubbly, stirring occasionally. Watch closely as the milk solids turn golden brown, which should take only a few minutes. When ready, remove from heat and transfer to a bowl, scraping any browned bits from the skillet.

For Streusel:

• In a separate bowl, mix together the flour, chopped pecans, oats, packed brown sugar, kosher salt, and ground pepper. Add the browned butter and stir until all ingredients are fully coated and combined.

For Casserole:

• Preheat your oven to 375°F. Generously grease your baking dish and set aside.
• Prepare the sweet potatoes by pricking them multiple times with a fork, then wrap each in foil and bake in the oven for about 50 minutes until soft.
• Core the Granny Smith apples, cutting them in half, and place them cut-side down on a foil-lined sheet pan. Bake together with the sweet potatoes for around 20 minutes until they are soft.
• Once the apples are cooked, scoop the flesh into a medium bowl, including any juices that may have leaked.
• After the sweet potatoes are cooled, remove their skins and mash the flesh. Combine the mashed sweet potatoes with the apple flesh in the bowl.
• In another bowl, mix together the melted butter, maple syrup, kosher salt, ground pepper, ground nutmeg, and lemon juice. Stir this mixture into the mashed sweet potatoes and apples until well-blended.
• Transfer the sweet potato and apple mixture into the prepared baking dish evenly.
• Spread the prepared streusel topping generously over the mashed mixture. You may have some streusel left for later use.
• Cover the dish with foil and place it on a baking sheet in the oven for 40 minutes.
• After 40 minutes, remove the foil and continue to bake for another 20 minutes or until the streusel is golden brown and the casserole reaches an internal temperature of 165°F.
• Allow the casserole to rest for about 10 to 15 minutes before serving, as it will hold its heat well.