braised beef short ribs with sherry & shiitake

Ingredients

• 3 pounds beef short ribs (about 8 to 10 pieces)
• 1 teaspoon ground himalayan sea salt, or to taste
• 1 teaspoon freshly ground black pepper, or to taste (i always use mixed peppercorns)
• 2 tablespoons olive oil
• 1 tablespoon clarified butter
• 2 1/2 cups red onions, sliced (lyonnaise cut)
• 2 1/2 cups shiitake mushrooms, sliced
• 3 large cloves garlic, pressed
• 1 tablespoon unbleached all-purpose flour
• 3 1/2 cups low-sodium beef broth, divided, or as needed
• 1/2 cup cooking sherry
• 2 tablespoons tomato paste
• 1 sprig rosemary
• 1 tablespoon balsamic vinegar
• 1/4 teaspoon cayenne pepper, or more to taste
• 1 tablespoon cornstarch mixed with 1/2 cup cold water
• 1 tablespoon fresh chopped parsley, for garnish