Heat a large skillet over medium heat with avocado oil. Add onion, carrot, and celery, cooking until softened, about 3–4 minutes. Stir in garlic and cook 30 seconds.
Add ground beef and cook until browned, breaking it apart with a spoon. Drain excess fat if needed.
Sprinkle flour over the beef mixture and stir to coat. Cook 1–2 minutes.
Stir in tomato paste and cook for 1 minute. Slowly add water, then mix in Better Than Bouillon Roasted Beef Base, red wine, Worcestershire sauce, brown sugar, thyme, bay leaves, salt, and pepper.
Simmer 20–30 minutes, stirring occasionally, until thickened. Remove bay leaves before assembling.
Let the filling cool slightly before topping with potatoes to prevent sinking.