Preheat Oven to 400°F (200°C)

Prepare the Mushroom Mousse:

• Heat 2 tablespoons of clarified butter in a pan over medium heat. 
• Add the finely chopped shallots and sauté until translucent.  
• Add the finely chopped mushrooms to the pan and cook until they release all their moisture and season with salt and pepper.  
• Remove the mushroom mixture from heat and let it cool. 
• Transfer the cooled mushroom mixture to a food processor.  Add the fresh tarragon leaves and chicken breast to the food processor.  
• Season with salt and pepper and process the mixture until smooth.
• If the mixture is too thick, add 1-2 tablespoons of cognac (or cream) to achieve a smooth, spreadable consistency.  
• Transfer the mushroom mousse to a pastry bag and refrigerate until needed.

Sear the Steaks:

• In another frying pan, heat clarified butter and when hot sear the steaks on all side quickly. If you like your steak medium rare to rare, sear it a bit longer if you like them more cooked.

Prepare the Sauce:

• In a saucepan, melt butter over medium heat. Add the finely chopped shallot and sauté until softened.  
• Add the fresh tarragon, wine and stock to the pan. Let it simmer until it reduces and thickens slightly.  
• Season the sauce with salt and pepper to taste.  
• If needed, thicken the sauce by adding the cornstarch mixture and stirring until it thickens further.  
• Finally, finish the sauce by whisking in 2-3 tablespoons of cold butter until it's fully incorporated. This will give the sauce a velvety texture.

Assemble the Individual Beef Wellingtons:

• Wrap each filet with 4 slices of the prosciutto ham the way the Chef did it in the video.   
• Cut out puff pastry circles that are slightly larger than your beef fillets
• Place one beef fillet on each puff pastry circle.  Pipe a layer of mushroom mousse on the base of the slice of Prosciutto cover with beef fillet, and top the filet with more mousse the same way the Chef did in the video. 
• Carefully fold the puff pastry over the beef and mushroom mousse, sealing the edges. Trim any excess pastry.
• Brush the top of each Wellington with a mixture of egg yolk.  Let it dry in the fridge for about 30 minutes.  
• Add about 1 teaspoon of heavy cream top the remaining egg yolk and apply one more layer on each filet for a shiny finish.
• Use a sharp knife to create decorative patterns on the puff pastry if desired.
• Place the prepared Wellingtons on a baking sheet lined with parchment paper or a silicone mat.
• Bake in the Preheated Oven for about 20-25 minutes or until the pastry is golden brown, and the internal temperature of the beef reaches your desired doneness (120°F-125°F or 49°C-52°C for medium-rare).
• Remove from the oven and let them rest for a few minutes before serving.
• Serve hot and enjoy your homemade Individual Beef Wellington!
• This recipe will surely impress your guests with its rich flavors and elegant presentation.
• It's perfect for a special dinner or holiday celebration. Bon appétit!