Prepare pasta as directed on the box, drain and drizzle 1-2 teaspoons of olive oil to prevent the noodles from sticking together and set aside. While pasta is cooking, prepare sausages.
Cut sausages into ½-inch thick slices. Heat a skillet over medium-high heat and add 1-2 tablespoons olive oil. Once the oil is hot, add sliced sausages and cook until a nice golden brown, turning every couple of minutes to make sure that each side is cooked, about 7-8 minutes. Remove sausages from pan and set aside.
In a large pot or skillet - I used the skillet from cooking the sausages - add butter, minced shallot and garlic. Cook over medium high heat until butter has completely melted.
Add in flour and whisk to combine. Slowly add in milk. Stir together and reduce heat to medium, bringing to a slow rolling bowl; stir often so the sauce does not burn to the bottom of the pan.
Once it is brought to a slow boil, add in the gruyere and parmesan cheese. Simmer over medium heat, and stir in the cooked sausages. Remove from heat and stir in pasta.
Serve. I garnish with a sprig of rosemary for color. You could also use basil or parsley. Enjoy!