Set a 2-quart saucepan on medium heat and add the oil. Once the oil is hot and shimmering, add the sausage and cook, breaking the sausage up with a wooden spoon, until it has rendered out and become browned and crispy, 6 to 8 minutes.
Add the porcini and a pinch of salt. When the mushrooms have released their liquid, scrape up the fond on the bottom of the pan, and then add the flour, stirring to coat all the ingredients. Continue gently stirring for about 1 minute and then add the cream, bring to a boil and then reduce to a gentle simmer. Simmer until the gravy is thickened and coats the back of a spoon, about 15 minutes. Season with salt and pepper.