Place a saucepan over a medium heat and heat the oil. Saute the onion until soft, roughly 7-8 mins. Add the sausage, breaking up with the back of a wooden spoon and cook until no pink remains. Add the garlic, red pepper flakes and thyme, and cook for 1 min more. Pour in the marinara and heavy cream, and simmer for 20 mins.
Remove from heat, add in lemon zest and adjust salt and pepper as needed. Best to let cool slightly before adjusting the salt and pepper.
For the Polenta
In a large saucepan over medium heat, bring milk to a simmer. Slowly whisk in semolina flour. Continue whisking until thickened, about 2 minutes. If too thick, continue to add milk until desired consistency. Remove from heat and stir in butter until melted, then add mascarpone and parmesan cheese. Season to taste with salt and pepper.
To Serve
Transfer polenta to a serving bowl with a heaping serving of the sausage ragu. Top with extra parmesan, and tons of freshly cracked black pepper. Garnish with fresh thyme.
Notes
Hot tips when it comes to freezing a ragu: it’s absolutely a great idea and once it’s fully cooked, transfer it to a freezer safe container and let it cool before putting on the lid. Then add the lid and store in the freezer for a few months.