1 (10-ounce) package frozen chopped spinach, defrosted and drained
1 (14-ounce) can artichoke hearts, chopped
Kosher salt and freshly ground black pepper, to taste
2 cups Monterey Jack Cheese - divided
Preheat broiler. Lightly oil a 9×13 baking dish or coat with nonstick spray.
In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
Heat a large skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes. Transfer to a paper towel-lined plate; set aside.
Heat olive oil in a medium pot over medium low heat. Add garlic and onion, and cook, stirring frequently, until the onions begin to soften, about 3-4 minutes. Whisk in flour until lightly browned, about 1-2 minutes. Gradually whisk in chicken broth and cook, whisking constantly, until incorporated, about 1-2 minutes. Stir in milk and bring to a simmer.
Add spinach and artichoke and stir until the sauce has thickened and the vegetables are heated through, about 2-3 minutes; season with salt and pepper, to taste. Stir in 1 1/2 cups cheese until smooth, about 1-2 minutes. Stir in penne and bacon.
Spread the penne mixture into the prepared baking dish. Sprinkle with remaining cheese. Place into oven and broil for 3-4 minutes, or until golden brown.