Preheat Oven:
* Preheat your oven to 350°F (175°C). 
Combine Ingredients:
* In a large bowl, combine the milk and egg. Whisk until blended. 
* Add the ground beef, stuffing mix, diced onion, ketchup, thyme, sage, salt, and pepper. 
* Gently mix with your hands or a spoon until well combined. Do not overmix.
Shape and Bake:
* Shape the meat mixture into a loaf and place in a baking dish or loaf pan. 
* Top the meatloaf with extra ketchup (optional).
* Bake for 50-60 minutes, or until the meatloaf is cooked through. The internal temperature should reach 160°F (71°C). 
Rest and Slice:
* Let the meatloaf rest for 10-15 minutes before slicing. This helps it hold its shape better. 
Serve:
* Slice and serve your Stove Top Stuffing Meatloaf hot.