Place the sausage links in a skillet and add enough water to come halfway up the sides of the links. Drizzle them with EVOO and bring to a boil over high heat. Lower the heat to medium and cook to evaporate the liquid and brown the links.
Bring a large pot of water to a boil, salt it, add the pasta and cook until al dente.
While the pasta is working, in a medium pot or deep skillet, melt the butter with 1 tbsp. EVOO, a turn of the pan. Add the fennel slices and fronds, the onion and garlic; season with salt and pepper. Cook, stirring, until softened, 10 to 12 minutes. Sprinkle the flour on top and stir for a minute, then add the wine to deglaze the pan. Stir in the stock and milk and cook to thicken, 5 to 7 minutes.
Stir 1 cup cheese into the fennel sauce to melt. Add the pasta and toss to combine. Serve the macaroni with the sausages and pass extra cheese around the table.