Remove and discard the tough stems from 1 pound kale. Stack the leaves and cut crosswise into 1-inch pieces.
Heat a large, straight-sided regular or cast iron skillet (at least 12 inches) over medium heat. Remove the casings from 1 pound Italian sausage. Add to the pan and use a wooden spoon to break the meat up into bite-sized pieces. Cook, stirring occasionally, until the sausage is cooked through and browned, 8 to 10 minutes.
Meanwhile, dice 1 small yellow onion (about 1 1/4 cups). Finely grate 1 ounce Parmesan cheese (about 1/2 packed cup), or measure out 1/3 cup store-bought grated.
Use a slotted spoon to transfer the sausage to a bowl. Add the onion to the pan (no need to wipe out) and stir to coat in the fat. If the pan is dry, add 1 tablespoon olive oil. Cook, stirring occasionally, until the onion is lightly golden brown around the edges, 3 to 5 minutes.
Add 1/2 teaspoon red pepper flakes if using and cook until the pepper is fragrant and lightly toasted, about 1 minute. Add the kale in batches and 1/4 cup of the low-sodium chicken broth. Toss with tongs and cook until the kale is wilted about 3/4 of the way down and a darker shade of green, 4 to 5 minutes.
Return the sausage and any accumulated juices in the bowl to the pan. Add 1 package soft garlic herb cheese and the remaining 3/4 cup chicken broth, and gently stir until the cheese is melted. Bring the mixture to a simmer.
Add 1 pound gnocchi and gently stir to combine. Return to a simmer and cook until the gnocchi begins to absorb the sauce and is heated through, 3 to 5 minutes. Add the Parmesan cheese and a few grinds of black pepper and stir to combine. If needed, add up to 1/2 cup more broth until a silky sauce forms that coats the pasta well.
Serve garnished with more Parmesan cheese and red pepper flakes if desired.