Step 1: Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
Step 2: In a large bowl, combine the cooked shredded chicken, softened cream cheese, and ranch dressing. Mix well until everything is thoroughly combined and creamy.
Step 3: Spread about ½ cup of the milk evenly in the bottom of the prepared baking dish.
Step 4: Lay 3 cooked lasagna noodles over the milk, slightly overlapping if necessary.
Step 5: Spread half of the chicken mixture evenly over the noodles.
Step 6: Sprinkle half of the cooked crumbled bacon over the chicken mixture. Follow with 1 cup of mozzarella cheese and ½ cup of cheddar cheese.
Step 7: Drizzle about ½ cup of milk over the cheese layer.
Step 8: Repeat the noodle, chicken mixture, bacon, and cheese layers (3 noodles, remaining chicken mixture, remaining bacon, 1 cup mozzarella, ½ cup cheddar).
Step 9: Place the final 3 lasagna noodles on top. Pour the remaining ½ cup of milk over the noodles and sprinkle with the remaining mozzarella cheese.
Step 10: Cover the baking dish loosely with aluminum foil. Bake for 25 minutes.
Step 11: Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown. If desired, you can broil for the last 2-3 minutes for an extra crispy top (watch carefully to prevent burning).
Step 12: Let the lasagna rest for 10-15 minutes before slicing and serving. This allows the layers to set, making it easier to cut.