Preheat the oven to 400°F. Spread the sesame seed bun cubes on a parchment-lined baking sheet. Drizzle with olive oil, toss to coat, and bake for 10 minutes until crispy.
In a large pot over medium heat, cook the ground beef with 2 tsp oregano, 2 tsp thyme, salt, and pepper until browned. Remove and set aside.
In the same pot, melt the butter over medium heat. Add onions, carrots, celery, salt, and pepper. Cook for 10 minutes over medium-high heat, stirring occasionally.
Reduce heat to medium, add garlic, remaining oregano, and thyme. Cook for another minute.
Stir in flour and cook for an additional minute. Deglaze the pot with a splash of chicken broth.
Add the rest of the chicken broth, macaroni, salt, and pepper. Bring to a simmer over medium-high heat, then reduce to low and simmer for 5-7 minutes until pasta is al dente.
Remove from heat. Stir in heavy cream and shredded cheese. Add white balsamic vinegar and the cooked ground beef. Heat for a few minutes until beef is warmed through. Season with salt and pepper.
Serve the soup with sesame seed bun croutons, garnish with green onions and cheddar cheese.
Notes
For a twist, try adding diced tomatoes or a pinch of red pepper flakes for some heat.