Prepare the rapini: Rinse the rapini, but don't dry. Cut the rapini bunch 2-3 inches from the top, removing and discarding the stem ends. (You're trying to get mostly the leaves and very little of the stem). Place rapini in a large pot on the stove-top over medium heat. Cook, stirring, until rapini is wilted, about 3 minutes. Place wilted rapini into a fine mesh strainer and press well to remove as much moisture as possible. Set aside.
In a food processor, combine the rapini, 1/2 of the artichoke hearts, the kidney beans, ricotta cheese, sour cream, Parmesan, 1/2 of the OKA cheese, olive oil, lemon juice, garlic and a bit of salt and pepper. Process until almost (but not completelsmooth. Transfer to a bowl. Roughly chop the remaining artichoke hearts and stir in. Taste mixture and add additional salt and pepper, as needed to heighten the flavours.
Spoon mixture into an 8 or 10-inch cast-iron skillet (or similar size oven-safe dish). Top with remaining OKA cheese.
Bake in preheated 350° F. oven until quite bubbly, about 35 minutes. If you'd like to brown up the top a bit, pop under the broiler for a few minutes at the end of cooking.
Serve warm with crostini or cut vegetables, such as carrots, broccoli or cauliflower.