Ingredients 3 tablespoons essential olive oil 1 onion, finely diced 1 large carrot, peeled and diced into 1/4-inch pieces 1 rib celery, trimmed and diced into 1/4-inch pieces Kosher salt and freshly ground pepper 8 ounces lean (8 percent fat) hamburger 3 garlic clove cloves, minced 1 tablespoon