Five Star Filet Mignon Recipe Stuffed with Mushrooms and Onions

Ingredients

• 1 cup plus 1/4 cup unsalted butter
• 1 finely chopped vidalia onion
• 1 tablespoon finely chopped fresh rosemary
• 4 cups (about 2 large mushrooms) diced portobello mushrooms
• 1/2 cup plus 1/4 cup dry white wine
• 6 (8 oz) about 2 inches thick filet mignon steaks
• Olive oil, for brushing
• 2 tablespoons finely chopped fresh tarragon
• 2 tablespoons champagne vinegar
• 1 clove minced garlic
• 1 minced shallot
• Kosher salt
• freshly ground Black pepper
• 4 egg yolks
• 1 tablespoon fresh lemon juice, optional