Heat the olive oil in a wide pot over medium-high heat. Add the sausage and cook for 15 minutes, breaking it up as it cooks. Once the sausage is completely cooked through, transfer it to a bowl.
Cook the aromatics:
Add the onion and sweet potato to the rendered fat from the sausage. Cook over medium heat for 8–9 minutes until just beginning to brown and soften. Season with salt and pepper.
Add the minced garlic and red Fresno chili pepper to the pot and cook for 1 minute.
Create a well in the middle of the vegetables and add the butter. Once melted and bubbly, add the oregano and thyme and let them sizzle in the butter for 30–45 seconds. Toss to coat the vegetables with spices.
Deglaze the pot:
Pour in the water, stock, or wine, and scrape up anything stuck to the bottom of the pot. Bring to a boil and then reduce heat.
Simmer the ragù:
Add the tomatoes and the cooked sausage to the pot. Add the maple syrup or sugar, and then season with salt and pepper. Simmer, uncovered, for 30–45 minutes. Stir the ragù occasionally, breaking up the tomatoes and lightly mashing the sweet potato as it cooks. Taste and season once more with salt and pepper.
Finish the ragù:
Taste the ragù and season once more. Add the chopped basil and the mascarpone cheese and cook for 5 minutes more.
Cook the pasta:
While the ragù simmers, bring a large pot of salted water to a boil and cook the rigatoni until al dente. Next, scoop out 1/2 cup of the pasta cooking water.
Sauce the pasta:
Drain the pasta and add it to the sauce and toss to coat. Add a bit of the pasta cooking water to thin out the sauce. You may not use it all! Turn off the heat once the pasta is glossy and coated with the sauce.
To serve:
Divide the pasta between shallow bowls and garnish with more basil. Add a drizzle of chili oil, if you like. Enjoy!