Beef Stroganoff with Dumplings

Name: Beef Stroganoff with Dumplings
Ingredients: 1 large yellow onion; 8 ounces cremini or button mushrooms; 2 cloves garlic; 1 pound boneless chuck or ribeye steaks; 1 1/2 teaspoons kosher salt, divided; 1/2 teaspoon freshly ground black pepper, divided; 1/4 cup sour cream; 4 tablespoons (1/2 stick) unsalted butter, divided; 1/4 cup dry white wine (optional); 1 tablespoon double concentrated tomato paste (from a tube); 2 tablespoons all-purpose flour; 2 cups low-sodium beef broth; 1 tablespoon Worcestershire sauce, plus more as needed; 1 tablespoon Dijon mustard; 1 teaspoon hot paprika; Small bunch fresh parsley; Small bunch fresh chives; 1 tablespoon freshly squeezed lemon juice; 1 cup all-purpose flour; 1 teaspoon baking powder; 3/4 teaspoon kosher salt; 1/2 cup whole milk; 1 tablespoon unsalted butter; Vegetable oil, for the baking sheet