Beef Wellington Bites

Heat a generous amount of olive oil in a substantial skillet over extremely high heat until it reaches a scorching temperature. Sear the filets on both sides until they are deeply browned, taking about 1 to 2 minutes per side. Remove the filets from the skillet and refrigerate them for at least an hour to ensure they are chilled.

In the same skillet, now warmed up over a moderate heat, melt a substantial amount of butter. Cook and stir the mushrooms, shallots, and garlic until the shallots are tender and translucent and the mushrooms have released their juices, taking around 6 to 8 minutes. Stir in 2 tablespoons of red wine, making sure to scrape and dissolve any browned flavor bits from the pan. Transfer the mushroom mixture into a bowl and refrigerate it for about 45 minutes.

Place two pieces of puff pastry on a clean work surface, and top each with a chilled filet. Spread half the mushroom mixture in an even layer on top of each filet, and top each with a piece of puff pastry. Fold and pinch the edges of the pastry together to seal in the contents, and trim to make a neat package. Cut a small slit into the top of each package.

Pour 1 and a half cups of red wine into a saucepan over medium heat, and let it simmer until the wine is reduced by half, taking about 15 minutes. Season the wine sauce to taste with salt and pepper. Meanwhile, whisk an egg into milk in a bowl, and brush the pastry packages with the egg mixture for a browner crust if desired. Return the bundles to the refrigerator to keep them chilled.

Preheat your oven to 450 degrees Fahrenheit (230 degrees Celsius). Line a baking sheet with parchment paper.

Place the puff pastry bundles onto the prepared baking sheet, and bake in the preheated oven until the pastry is golden brown and crisp, and the filets are cooked to your desired level of doneness (for medium-rare, about 15 minutes; an instant-read thermometer inserted into the center should read 130 degrees Fahrenheit (54 degrees Celsius)). Serve each filet in its pastry shell with a spoonful of wine sauce on top.