Preheat the oven to 350°F. Line a large baking sheet with foil and coat with nonstick spray.
Peel sweet potatoes and slice into ¼–½-inch thick rounds. Arrange in a single layer on a prepared sheet.
In a small bowl, combine melted butter, brown sugar, and cinnamon. Brush mixture over both sides of the sweet potato slices.
Bake for 15–20 minutes, until fork-tender (time will vary by thickness).
While baking, cut marshmallows in half.
Remove potatoes from the oven. Top each round with a marshmallow half, cut side down.
Return to the oven 1–2 minutes, just until the marshmallows puff. Watch closely—they burn quickly.
Immediately top each marshmallow with a pecan half.
Serve warm.
Notes
Use sweet potatoes that are roughly the same size so baking is even.
Brush the glaze well on both sides so you get flavour in every bite.
Watch the marshmallows very closely in the final step — they can go from golden to burnt in a matter of seconds.
Storage & Reheating Tips
Refrigerate: Store any leftover bites in an airtight container in the fridge for up to 3 days.
Reheat: Preheat oven to 325°F and warm on a baking sheet until heated through (about 5-10 minutes, depending on quantity). Avoid microwaving if possible—microwaving can soften or collapse the marshmallows.
Make-ahead tip: You can peel, slice, and roast the sweet potato rounds ahead of time (stop just after they become fork-tender). When ready to serve, top with marshmallows and pecans, and finish toasting for the last 1-2 minutes.