Here is another quick & easy chicken casseorle. You can use spinach or swiss chard instead of the kale if you prefer.
¾ lb. pasta shells
2 tbsp. unsalted butter
1 large yellow onion
3 clove garlic
2 bunch kale
2 c. shredded or chopped cooked chicken
1 container part-skim ricotta
3 tbsp. finely grated lemon zest
¾ c. grated Parmesan
Preheat oven to 350 degrees F. In a large pot of boiling salted water, cook pasta according to package instructions. Drain; return to pot. In a large skillet, melt butter over medium-high. Add onion and garlic; cook until onion is beginning to soften, 4 minutes. Add kale, cover, and cook until almost tender, about 5 minutes. Transfer to pot with pasta.
Stir in chicken, ricotta, lemon zest, and 1/2 cup Parmesan; season with salt and pepper. Transfer mixture to a 9- by 13-inch baking dish; top with 1/4 cup Parmesan. Bake until top is golden, 30 minutes.