Heat a large pot of well salted water over high heat for the pasta.
While the water is coming to a boil, begin making the sauce. Slice each sausage lengthwise. Then place the slices cut side down and slice the lengthwise pieces. The slices will look like half moons.
Over medium high heat, heat 1 Tablespoon olive oil in a sauté pan large enough to hold the pasta and sauce. Add the sliced sausage and brown stirring occasionally. Once the sausage is browned, turn off the heat and put the sausage in a bowl and set aside.
Return the pan to the stove and turn the heat to medium. Add the diced onion and sauté for about 4 minutes. Add the garlic and sage and sauté for a few more minutes. Add 1 teaspoon salt.
Reserve about 1 cup of the pasta cooking water.
Add 1 ½ cups chicken stock to the pan and bring to a simmer. Allow the stock to simmer for about 5 minutes or has reduced by half.
Once the water comes to a boil, add the pasta and cook until aldente. (I cook the pasta just a few minutes less than the package directions). When the pasta is cooked drain it and reserve about 1 cup of the pasta cooking water.
Rinse and tear the kale. Add it to the sauté pan along with the browned sausage you set aside earlier. Allow it to simmer for a few minutes or until the kale turns bright green.
Turn off the heat under the sautè pan. Add the cooked pasta and the grated cheese and stir. Scrape the bottom of the pan periodically to catch any cheese that might stick to the bottom.
Add some of the reserved pasta water and stir again. Add a few turns of freshly ground pepper. Taste and adjust add more salt and pepper if needed.
Optional - Serve with some additional grated cheese.
Notes
* Cook the pasta aldente because you're adding it to a sauce. The cooked pasta will absorb the sauce and may become too soft if you cook it as long as the package suggests. I just cook the pasta a few minutes less than the directions on the package.** You can use more or less kale (or another green). *** You can use less cheese if you prefer.