When ready to cook, remove the sausage mixture from the refrigerator and, using clean hands, form into four 1/2-inch-thick patties (don't worry about making them perfectly round as they will get broken up into smaller pieces; if using store-bought sausage, form uncased sausages into 1/2-inch-thick patties).
In a large skillet or straight-sided sauté pan, heat the oil over medium-high heat until shimmering.
Add the sausage patties and cook until the bottom side is light golden brown, 3 to 5 minutes.
Using a thin metal spatula, turn the sausage patties onto the uncooked side, leaving an open area in the center of the skillet.
Add the onion, lower the heat to medium, and cook, using a wooden spoon to break up the sausage into 1/2- to 1-inch pieces, until the sausage is just cooked through and the onion is softened, about 2 minutes; lower heat at any point if sausage or onion threaten to scorch.
Increase the heat to medium-high and add the wine.
Bring to a simmer and cook, swirling the pan and scraping up any stuck-on bits with a wooden spoon, until the wine is reduced by roughly half, about 30 seconds.
Add the cream, bring to a simmer, and cook, stirring frequently to keep the cream from scorching on the sides of the pan, until the sauce is slightly thickened, 3 to 5 minutes.
Season with salt and pepper to taste and reduce the heat to the lowest possible setting to keep the sauce warm and prevent it from over-reducing.