Preheat the oven to 350 degrees F. Spray a 9-by-13-inch baking dish with nonstick cooking spray and set aside.
In a large pot or Dutch oven, combine the half-and-half and 6 cups of the chicken stock and bring to a boil over medium-high heat. Once up to a boil, stir in the grits. Bring it back up to a boil, and then reduce the heat to low and cover. Simmer, stirring frequently, until the mixture has slightly thickened (it should resemble cooked oatmeal in thickness), 10 to 15 minutes. Use a whisk to break up any lumps that have formed.
Meanwhile, in a large saucepan, cook the bacon over medium-high heat until just turning crispy, about 7 minutes. With a slotted spoon, remove the bacon and place it on a paper towel, patting it to remove any excess fat. Using the same saucepan, add the onions to the leftover bacon drippings and saute until translucent, 5 to 7 minutes. Then add the collard greens and the remaining 2 cups chicken stock and cook until tender, another 10 minutes. Drain the collards and onions in a colander.
Once the grits are done, add the Parmesan, butter, salt, pepper and 1/2 cup of the Monterey jack. Stir until the butter has melted and all the ingredients are well combined. Then add the drained collards mixture and stir.
Transfer the grits mixture to the prepared baking dish and top with the crumbled bacon and the remaining 1/2 cup Monterey jack. Bake until the cheese is melted and bubbly, about 15 minutes.