Mushroom and Shallot Salisbury Steak

Name: Mushroom and Shallot Salisbury Steak
Ingredients: ¾ cup panko breadcrumbs; 1 Tbsp. plus 2 tsp. Worcestershire sauce; 5 medium shallots, 2 finely chopped, 3 thinly sliced; 1 large egg; 1 lb. ground beef; 9 garlic cloves, finely grated, divided; 3 tsp. mustard powder, divided; 2½ tsp. Diamond Crystal or 1½ tsp. Morton kosher salt, divided, plus more; 1½ tsp. freshly ground pepper, divided, plus more; 2 Tbsp. extra-virgin olive oil; 4 Tbsp. unsalted butter; 1 lb. crimini mushrooms, thinly sliced; 3 Tbsp. all-purpose flour; 3 cups low-sodium chicken broth; Juice of 1 lemon; 5 sprigs thyme; ¼ cup coarsely chopped parsley