As much as Chicago is a great sausage city, it's still a rare occurrence to see it house-made on menus in restaurants. Making it is a huge hassle requiring good technique and special equipment, not to mention special-ordered casings and lots of room.
But there is one regular exception to this rule, and that's breakfast sausage. Lots of places make it—mostly because there's no need for casings or a sausage stuffer. You can make a large batch or a small one, shape it into patties, and fry it up. I'm often on the lookout for examples of it done well.
At Vincent in Andersonville, it's served on their brunch menu, most simply with eggs, toast, and glorious roasted fingerling potatoes in their very lovely room or on the patio.
They make a very honest sausage, which I like—a straightforward porky flavor that's not heavily spiced with sage and black pepper like breakfast sausage often is. In fact, when I asked about its seasoning, my waitress disappeared for a few minutes before reappearing with a large notebook (the kitchen's recipes) wherein I learned that sage, rosemary, brown sugar, nutmeg, red peper flakes, and cayenne all make their way into the proceedings. Once cooked, it has a salty, nicely crisp exterior.