Twice-baked sweet potatoes with leeks and sausage

My amazing friend Beth made these for me last week, and then we made them for company tonight and they are amazing.  This is a savory sweet potato recipe that tastes like delicious fall.  This is for sure a new favorite.  It comes from Fine Cooking Magazine.

Twice-Baked Sweet Potatoes with Leeks and Sausage

4 small sweet potatoes (about 8 oz. each)
1 Tbs. olive oil
1/2 lb. bulk sweet Italian sausage (or link sausage, casings removed)
1 Tbs. unsalted butter
1 lb. leeks, white and light-green parts only, quartered lengthwise and thinly sliced (about 2 cups)
1 tsp. chopped fresh sage
1/4 tsp. chopped fresh thyme
Kosher salt
1/2 cup sour cream
1/4 cup grated Gruyère

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Tip: Sweet potatoes have thin, delicate skin that tears easily, so don’t scrape too hard when scooping them out. Leaving 1/8 inch of flesh in each shell will  keep it from flopping closed.

Position a rack in the center of the oven and heat the oven to 375°F. Line a heavy-duty rimmed baking sheet with parchment or foil.Poke the sweet potatoes a few times with the tip of a knife and arrange them on the baking sheet. Bake until completely tender when pierced in the fattest part with a skewer, 35 to 60 minutes.Meanwhile, heat the oil in a 10-inch skillet over medium-high heat. Add the sausage, reduce the heat to medium, and cook, breaking it into small bits with the edge of a slotted spoon, until no longer pink, 5 to 6 minutes. Transfer to a plate and set aside. Pour off all but 1 Tbs. of the fat and add the butter. When it melts, add the leeks, sage, thyme, and 1-1/2 tsp. salt. Cook, stirring stirring, until the mixture just starts to sizzle. Reduce the heat to low and cook, stirring frequently, until the leeks are very soft and starting to turn golden, 10 to 15 minutes. When the sweet potatoes are cool enough to handle, carefully cut them in half lengthwise and gently scoop the flesh into a medium bowl, leaving about 1/8 inch of flesh in the shells. Mash the scooped flesh with a fork or potato masher until smooth. Stir in the sour cream and 1 tsp. salt. Fold the sausage and leeks into the mashed sweet potato and season to taste with salt. Position a rack 6 inches from the broiler element and heat the broiler on high. Mound the filling into the potato skins and top with the cheese. Put the potatoes in a 9×13-inch baking dish and broil until the cheese is golden, about 4 minutes. Serve immediately.