Easy Individual Beef Wellington with Caramelized Onions

Name: Easy Individual Beef Wellington with Caramelized Onions
Ingredients: • 2 tablespoons olive oil; • 2 tablespoons unsalted butter; • 2 large yellow onions, cut in half and thinly sliced; • 1/4 cup dry sherry wine; • 1/2 cup homemade or prepared beef broth (low-sodium); • 1 pound button or crimrni mushrooms, dry brushed and sliced; • 2 tablespoons freshly chopped parsley; • 1 tablespoon fresh thyme leaves; • 6 4-ounce center-cut uniform filet mignon steaks; • 12 5by 5-inches Puff pastry squares; • Dijon mustard (1teaspoon per pastry square); • 1 extra large egg yolk + 2 teaspoons water for eggwash