Preheat your oven to 350°F (175°C) and butter a 9x13 baking dish.

Peel and cube the sweet potatoes into roughly 1–1½ inch pieces so they cook evenly.

Measure out the rest of your ingredients (butter, sugars, eggs, milk, spices, streusel ingredients) so everything’s ready to go — it makes the next steps smooth and calm.

Pro tip: Start your potatoes in cold water (see next step) — it helps them cook evenly from edge to center.

Place the cubed sweet potatoes in a large pot and cover with cold water by about an inch.

Bring to a gentle boil over high heat, then reduce to a simmer. Cook until the pieces are fork-tender — about 12–15 minutes depending on size.

Drain well in a colander, then return them to the warm pot off the heat for a minute to let excess steam evaporate. This keeps the filling from getting watery.

Pro tip: Don’t overcook until they’re falling apart — you want tender, not mushy. Drying them briefly in the warm pot makes the mash richer and not runny.

Transfer the drained potatoes to a mixing bowl (or keep in the pot). Add the ½ cup melted butter, ½ cup granulated sugar, 2 beaten eggs, ½ cup milk, vanilla, cinnamon, nutmeg, and a pinch of salt.

Use a hand mixer on medium speed for 1–2 minutes until smooth and fluffy. If you prefer, mash by hand with a potato masher and then beat briefly to incorporate air.

Taste and adjust — if you like it a touch sweeter or a bit more spice, now’s the time to tweak. The texture should be velvety and scoopable, not soupy.

Pro tip: A hand mixer gives the lightest, airiest texture. Mix just until combined — overbeating can make the filling too loose.

In a separate bowl, combine ½ cup flour, ½ cup packed brown sugar, and ½ cup chopped pecans.

Add the 4 tablespoons softened butter and use a fork, pastry cutter, or your fingertips to work the butter into the dry mix until you have coarse crumbs and some pea-sized bits.

Leave a few slightly larger pecan pieces — they give satisfying crunch after baking.

Pro tip: For a slightly chewier streusel, stir in a couple tablespoons of old-fashioned oats. (Totally optional — the classic pecan streusel is wonderful as written.)

Spread the sweet potato mixture evenly in your prepared 9x13 dish, smoothing the top with a spatula.

Sprinkle the streusel evenly over the sweet potatoes, covering the surface but leaving a little texture — don’t press it flat.

If you like a thinner streusel, reserve a couple of tablespoons and scatter them on top for visual contrast.

Place the casserole on the middle rack and bake at 350°F (175°C) for 25–30 minutes, or until the streusel is golden and you see a gentle bubbling around the edges.

If the topping is browning faster than the center is warm, tent loosely with foil and continue baking until heated through. For an extra-crisp finish, slide under the broiler 1–2 minutes — watch it like a hawk.

Pro tip: Use a toothpick in the center to check warmth — it should come out hot and moist. Tent with foil if needed to prevent over-browning.

Let the casserole rest for 10–15 minutes before serving — this helps the filling set so it slices prettily.

Serve warm and watch the smiles. This is perfect as a Thanksgiving sweet potato casserole or anytime you want cozy, comforting sides.

To make this a true make ahead sweet potato casserole, assemble it up to 24 hours in advance: cover tightly and refrigerate. When ready to serve, take it from fridge to oven and add about 10–15 minutes to the baking time (still at 350°F/175°C) until heated through.

You can also assemble and freeze unbaked for up to 2 months. Thaw overnight in the fridge before baking.

Store leftovers in an airtight container in the fridge for up to 4 days; reheat covered in a 325°F (160°C) oven until warmed through.

Pro tip: If baking straight from the fridge, let the casserole sit at room temperature for 20–30 minutes before putting it in the oven — it helps it bake evenly and reduces extra baking time.