Preheat oven to 375 degrees. In a frying pan, heat and melt butter with olive oil. Add yellow onion and sauté until softened and translucent, about 5 minutes. Add kale and cook until kale wilts, about 1 to 2 minutes.
Place cooked contents, garlic and artichokes into a food processor and pulse for several seconds. Transfer mixture to a medium bowl.
Add in the spinach, sour cream, mayonnaise, grated parmesan cheese, salt, and cayenne pepper. Mix all the ingredients together. Taste and add fresh cracked pepper to taste. Stir in 1 cup of shredded mozzarella.
Place mixture into a deep 8x8 baking dish or 4 ramekins. Bake uncovered for 20-25 minutes.