Savory Hand Pies

Ingredients:
1 tablespoon olive oil
1 tablespoon butter
1 onion, finely diced
1 carrot, peeled and finely diced
1 rib celery, finely diced
Salt
Black pepper
4 cloves garlic, pressed through garlic press
1 pound ground beef (85/15 ratio lean to fat)
1 ½ teaspoons Italian seasoning
½ teaspoon white pepper
1 tablespoon tomato paste
2 tablespoons Worcestershire sauce
3 level tablespoons all-purpose flour
1 ¼ cups beef stock or broth
1 medium russet potato, peeled and diced into ¼ -½ inch cubes
2 teaspoons fresh thyme leaves, plus extra for garnish