Bring a large pot of water to a boil. Season with salt, but avoid making it overly salty since a significant amount of the pasta water will be added to the sauce.
kosher salt
Melt the butter in a medium skillet over medium heat. Add the sage leaves and fry until dark green and crisp, about 30-60 seconds. Use a slotted spoon to transfer the sage to a paper towel-lined plate.
4 tablespoons butter, 12-15 sage leaves
Continue cooking the butter until the milk solids turn golden brown and smell nutty, about 1 minute. Immediately add the panko and cook, stirring frequently, until the breadcrumbs are crisp and evenly browned, about 2-3 minutes. Transfer to a bowl. Crumble half of the fried sage into the breadcrumbs and reserve the remaining leaves for serving.
⅔ cup panko breadcrumbs
Add the sausage to a large skillet over medium-high heat. Cook, breaking it into small pieces, until well browned and cooked through, about 8 minutes.
1 pound sweet Italian sausage
Push the sausage to one side and reduce the heat to medium. Add the shallot and thyme and cook until softened, 3-4 minutes. Add the garlic and cook until fragrant, about 30 seconds more.
1 shallot, 2 teaspoons thyme, 3 garlic cloves
Pour in the wine and scrape up any browned bits from the bottom of the pan. Simmer until the wine has reduced by at least half, about 2-3 minutes. Reduce the heat to low.
½ cup dry white wine
Add the pasta to the boiling water and cook until just shy of al dente. Reserve at least 3 cups of the starchy pasta water before draining.
12 ounces pumpkin-shaped pasta
Add the pumpkin, black pepper and 1 cup of pasta water to the skillet. Stir until smooth, then simmer until the sauce has reduced slightly and the pumpkin no longer tastes raw, about 3-4 minutes.
1 cup pumpkin puree, ½ teaspoon freshly ground black pepper, 3 cups reserved pasta cooking water
When the pasta is still very al dente, about 2-3 minutes before the package directions indicate, drain and transfer it directly to the pumpkin sauce.
Cook over medium heat, tossing frequently, until the pasta is al dente and the sauce clings to it, about 2-3 minutes. Add more pasta water as needed, about ¼ cup at a time. The sauce should stay on the looser side because it will continue to thicken.
Turn off the heat, then add the mascarpone and Parmigiano. Toss until the cheeses are melted and the sauce is completely smooth. Add more pasta water as needed to maintain a loose, creamy consistency. Taste and adjust the seasoning as needed.
8 ounces mascarpone cheese, 2 ounces Parmigiano Reggiano
Divide the pasta among four bowls. Top with the brown butter breadcrumbs, reserved fried sage leaves, and additional Parmigiano. Serve hot.