Heat olive oil in a 5 or 6-quart Dutch oven over medium-high heat. Add red onion, carrots, and celery and cook, stirring frequently, until the vegetables are tender and nicely caramelized, approximately 8-10 minutes.
Add the chopped porcini mushrooms and sausage and cook until sausage is no longer pink inside, stirring frequently while breaking the sausage into small pieces with a wooden spoon.
Add the ground beef and cook until browned. When finished, carefully drain and discard any excess fat from the pot, if necessary.
Add the wine and scrape up any brown bits from the bottom of the pan with a spatula or wooden spoon. Once the wine is reduced by half, add the tomatoes and the liquid from reconstituting the mushrooms. Stir to combine and season with salt and black pepper, to taste.
Reduce heat to just below medium and continue cooking, stirring occasionally, for another 45-50 minutes. If sauce becomes too dry, add a little water while it cooks.
Remove from heat and serve immediately on top of a bed of warm, creamy polenta or spoon on top of a grilled polenta wedges for a tasty appetizer.