Step 1: Cook the pasta. Heat the oven to 350 degrees F and grease a 9x13 inch baking dish. Boil the pasta for 2 minutes less than the package directs, then drain.
Step 2: Cook the bacon. Cook the bacon in a skillet until crisp, drain on paper towels, and crumble.
Step 3: Make the sauce. In a large bowl, whisk the soup, milk, ranch dressing, and ranch seasoning until smooth.
Step 4: Combine. Fold in the pasta, chicken, half the bacon, the peas or broccoli if using, and 1 cup of the cheese.
Step 5: Top and bake. Spread into the dish and top with the remaining cheese and bacon. Cover with foil and bake for 20 minutes, then uncover and bake 10 minutes more, until bubbling and golden and hot in the center (165°F / 74°C).
Step 6: Rest and serve. Rest for 5 minutes, then top with green onions.
