Step 1: Preheat the Oven
1. Preheat Oven: Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease a loaf pan.

Step 2: Prepare the Onions
1. Sauté Onions: In a skillet over medium heat, add the olive oil. Add the chopped onion and sauté until softened and caramelized, about 8-10 minutes. Add the minced garlic and cook for an additional minute. Remove from heat and let cool slightly.

Step 3: Prepare the Meatloaf Mixture
1. Combine Ingredients: In a large bowl, combine the ground beef, sautéed onions and garlic, breadcrumbs, milk, eggs, Worcestershire sauce, Dijon mustard, salt, pepper, and thyme (if using). Mix until just combined; do not overmix.

Step 4: Shape the Meatloaf
1. Form the Loaf: Transfer the meat mixture to the prepared baking sheet or loaf pan. Shape it into a loaf, smoothing the top and sides.

Step 5: Prepare the Glaze
1. Mix Glaze Ingredients: In a small bowl, combine the French onion soup, brown sugar, and Worcestershire sauce. Mix well.

Step 6: Bake the Meatloaf
1. Add Glaze: Pour half of the glaze over the top of the meatloaf, spreading it evenly.
2. Bake: Bake in the preheated oven for 45-50 minutes, or until the internal temperature reaches 160°F (70°C).
3. Add More Glaze: In the last 10 minutes of baking, add the remaining glaze on top of the meatloaf.

Step 7: Serve
1. Cool and Slice: Allow the meatloaf to rest for about 10 minutes before slicing. Serve warm with your favorite sides.