Wash kale, and remove stems and tough central rib. Cut or tear leaves into strips, roughly 1/2 to 1 inch wide.
Blanch kale in a large pot of boiling water just until the color changes to bright green, about 1-2 minutes (don't overcook!). Use a slotted spoon to remove kale to a plate or bowl and set aside. (Don't drain the greens too thoroughly. You want to allow a little liquid to accumulate in the dish while they rest).
Leave the cooking water in the pot and continue to boil. Add pasta and cook to al dente. Drain and set aside when done.
While pasta is cooking, heat a large skillet over medium heat. Add the oil. Once heated, add the butter or ghee and melt to combine with the oil (if using butter, cook until it stops foaming). Add garlic and saute until fragrant, 1-2 mins.
Reduce heat to medium-low and add kale and any accumulated liquid to the pan. Toss to combine. Add beans, salt, pepper, herbs, and pepper flakes (if using). Toss well, then allow to simmer until beans are heated through and liquid has reduced somewhat, about 5 mins.
Using a fork, mash about a third of the beans in the skillet to form a paste. Add the lemon juice and combine thoroughly. Remove from heat and toss with pasta.
Serve topped with grated Parmesan and red pepper flakes, if desired.