Ingredients:

  • 4 lbs Sweet Potatoes (Orange variety, e.g., Garnet or Jewel)
  • 1/2 cup Unsalted Butter (melted, for filling)
  • 1/4 cup Light Brown Sugar (packed, for filling)
  • 1/4 cup Heavy Cream (or evaporated milk)
  • 2 Large Eggs
  • 1 teaspoon Vanilla Extract
  • 1 teaspoon Ground Cinnamon (for filling)
  • 1/2 teaspoon Ground Nutmeg
  • 1/2 teaspoon Salt (Fine grain, for filling)
  • 1 cup All-Purpose Flour
  • 1/2 cup Light Brown Sugar (packed, for streusel)
  • 1/4 cup Rolled Oats (not instant)
  • 1/2 cup Chopped Pecans (or walnuts)
  • 1/2 teaspoon Ground Cinnamon (for streusel)
  • Pinch Kosher Salt (for streusel)
  • 6 tablespoons Unsalted Butter (cold, diced, for streusel)
  • 4 cups Mini or Large Marshmallows (about 10 oz)

Instructions:

  1. Prep the Sweet Potatoes: Peel the sweet potatoes and cut them into uniform 2-inch chunks. Place in a large pot, cover with cold water, and add a generous pinch of salt. Bring to a boil, then reduce heat and simmer until fork-tender (about 20–25 minutes).
  2. Drain and Mash: Drain the potatoes thoroughly. Immediately mash the potatoes using a potato masher, or press through a potato ricer for the smoothest possible texture. Set aside to cool slightly.
  3. Brown the Butter: Melt the 6 tablespoons of butter (for the streusel) in a small saucepan over medium heat. Continue cooking, stirring occasionally, until the milk solids turn golden brown and nutty-smelling (about 3–5 minutes). Immediately pour the brown butter into a small bowl to stop the cooking process and allow it to cool slightly.
  4. Prepare the Streusel: In a medium bowl, combine the flour, brown sugar (1/2 cup), oats, pecans, cinnamon (1/2 tsp), and salt. Pour the slightly cooled brown butter over the dry ingredients. Use your fingers or a fork to mix until the mixture resembles coarse, buttery crumbs. Refrigerate the streusel while preparing the filling.
  5. Mix the Wet Filling: Preheat the oven to 375°F (190°C). Grease the 9x13 inch casserole dish. In a separate bowl, whisk together the melted butter (1/2 cup), eggs, cream, vanilla extract, brown sugar (1/4 cup), cinnamon (1 tsp), nutmeg, and salt until well combined.
  6. Combine the Filling: Add the wet mixture to the mashed sweet potatoes. Mix thoroughly (using a spatula or hand mixer) until the filling is homogenous, light, and smooth. Do not overmix, but ensure no lumps remain.
  7. Transfer and Bake: Pour the sweet potato filling into the prepared casserole dish and smooth the top with a spatula.
  8. Initial Bake: Bake for 30–35 minutes, or until the edges are just set and the centre has puffed slightly.
  9. Apply Streusel: Remove the casserole from the oven. Evenly crumble the chilled brown butter streusel over the entire surface of the sweet potato base.
  10. Partial Streusel Bake: Return the casserole to the oven for 5 minutes to allow the streusel to set and become fragrant.
  11. Add Marshmallows: Carefully layer the marshmallows (or cut halves) over the streusel topping, ensuring good coverage.
  12. Toast and Finish: Return the casserole to the oven, or switch the oven to the broiler setting (watching very closely). Cook for 3–5 minutes until the marshmallows are golden brown and toasted. (If using the broiler, keep the dish rack low and watch constantly to prevent burning.)
  13. Rest and Serve: Allow the casserole to rest for 10 minutes before serving. This helps the filling solidify and makes serving easier.