Preheat the oven to 425 F and grease a large baking sheet with olive oil.
In a medium light-coloured saucepan, melt the butter over medium heat. Continue cooking the butter, swirling the pan frequently, until it starts to turn golden and smell nutty, and brown bits have started to collect at the bottom of the pan. Keep a close eye on it, it can burn quickly. Remove from heat.
Immediately whisk in the maple syrup and red pepper flakes.
Toss the sweet potatoes with 1/2 of the browned butter glaze, a large pinch of salt and a few grinds of fresh pepper, and spread in one layer on the prepared baking sheet.
Roast the sweet potatoes, for about 35-40 minutes, tossing with a spatula once, about halfway through, until caramelized and tender.
Pour the remaining brown butter maple glaze over the sweet potatoes and toss gently to coat. Sprinkle with parsley and additional salt and pepper if desired, and serve.
Video
Notes
Feel free to reduce the maple syrup or eliminate it if you prefer a more savory dish.
To give it a bit more kick, increase the crushed red pepper to taste, or add a dash of hot sauce or pinch of cayenne to the glaze.
To make this ahead, you can either 1) prep the sweet potatoes and glaze separately and store in the refrigerator until ready to roast, or 2) roast the sweet potatoes as described, but save the remaining half of the glaze in an airtight container in the refrigerator until ready to use. Reheat the sweet potatoes in a 400F oven for 10-15 minutes until heated through. Reheat the glaze in the microwave for a few seconds and toss with the potatoes.