Heat a medium pot of salted water to boiling on high.
Fry the rosemary & walnuts:
In a large pan, heat a thin layer of oil on medium-high until hot. Once the oil is hot enough that a rosemary leaf sizzles immediately when added to the pan, add the rosemary and walnuts. Cook, stirring frequently, 2 to 3 minutes, or until the rosemary is crispy and the walnuts are golden brown. Leaving any oil in the pan, transfer the fried rosemary and walnuts to a paper towel-lined plate. Immediately season with salt and pepper.
Add the pasta to the pot of boiling water; cook according to package instructions or until al dente (still slightly firm to the bite). Reserving 1/2 cup of the pasta cooking water, drain thoroughly.
Cook the kale:
Add 2 teaspoons of olive oil, the shallot, and the garlic to the pan; season with salt and pepper. Cook on medium-high, stirring occasionally, 2 to 3 minutes, or until softened and fragrant. Add the kale and as much of the red pepper flakes as you’d like, depending on how spicy you’d like the dish to be; season with salt and pepper. Cook, stirring frequently, 3 to 4 minutes, or until the kale has wilted. Add the vinegar (be careful, as the liquid may splatter) and cook, stirring constantly, 30 seconds to 1 minute, or until the liquid has cooked off. Add the heavy cream and cook, stirring constantly, 30 seconds to 1 minute, or until thoroughly combined. Turn off the heat and season with salt and pepper to taste.
Add the cooked pasta, butter, and half the reserved pasta cooking water to the pan of cooked kale. Cook on medium-high, stirring vigorously, 1 to 2 minutes, or until the pasta is thoroughly coated. (If the pasta seems dry, gradually add the remaining cooking water to achieve your desired consistency.) Turn off the heat and season with salt and pepper to taste. Divide the finished pasta between 2 dishes. Drizzle with olive oil. Top with the fried rosemary and walnuts. Garnish with the cheese. Enjoy!