1. Open the beef fillet and wipe it with paper towels. 

2. Remove the excess fibers and place it in a baking tray. Marinate with olive oil, salt, pepper and thyme.

3. Place a non-stick frying pan over medium-high heat and once it is hot, add the fillet (if it doesn't fit, cut it in half) and sear it on all sides until golden brown, for about 5-7 minutes. Remove it from the pan and place them on a wire rack and let them rest for 5 minutes.

4. Brush the fillet with the mustard and bake in a preheated oven at 200°C for 20-30 minutes. For optimal results, use a meat thermometer—once the internal temperature reaches 55-57°C (130-135°F), remove the fillet from the oven and let it rest for 5 minutes before serving.

5. For the mushroom ragout, place a pot over medium-high heat. Add the olive oil, onion, garlic and sauté until golden brown. 

6. Then place the mushrooms in the pot, season with salt and pepper and cook over high heat until they are browned and all the liquid has evaporated.

7. Add the mustard, stir and add the wine. Continue cooking for 2-3 minutes. Finally, add the cream and bake until the ragu thickens.

Kali Orexi!