1. Season tenderloin thoroughly with salt and pepper, wrap it well with plastic wrap and towel, and store it in the refrigerator. (I've set aside two days to give you enough time, but if you want to do it quickly, you can use it right away.) The reason for wrapping it with a towel is to prevent the shape of the meat from sagging. (You can tie it with a strap, but the towel stays prettier.)

2. Place olive oil in a heated frying pan over high heat. Bake until all sides of tenderloin are brown. I baked for a total of 18 minutes, 3 minutes per side. Transfer to dish and cool, cover all sides with Dijon mustard. And wrap it well with plastic wrap, and spend the day in the refrigerator again.

3. The next day, you create Duxelles. Prepare mushrooms, shallots (instead of onions), and thyme by mincing them well. Melt the unsalted butter in a well-heated frying pan. Then cook the prepared mushrooms, shallots, and thyme until the liquid evaporates. I cooked it on medium heat for an hour and 45 hours. Season with salt and pepper. I didn't season this part because I put enough on the tenderloin. And it cools down well. If you do it again next time, I'll cook it until it dries more water.

4. While Duxelles is cooling, cover the floor with enough wrap to cover the tenderloin, cover the length of the tenderloin, and cover it with enough prosciutto to roll. I've laid out 8 sheets, so you can use them according to your preference.

Place tenderloin on top of mushrooms and roll well with plastic wrap and towel. And wait in the refrigerator for a while

6. Heat the oven to 425F (220 degrees).

7. Prepare the pastry. It also makes it big enough to cover the tenderloin well.

Use an egg wash (I just used the yolk) to cover the tenderloin well with pastry.

9. Pastry decoration is optional.

Cook the finished tenderloin for 40 to 45 minutes in the oven at 425F (220 degrees). The internal temperature is 120F (approximately 50 degrees) when medium rare is targeted. I just wanted medium, so I cooked it for 45 minutes at 425F, then another 10 minutes at 225F (about 110 degrees). Rest for 10 minutes after cooking.