How to make
Make small cuts in the turkey fillet (big enough to fit a 1/4″ (0.5 cm) cube inside). Cut the carrot, garlic and butter into small cubes and stuff them in the openings you made. Sprinkle the meat with salt and black pepper as desired, pour on 1 tbsp soy sauce and leave for a few hours in the fridge (covered with foil or in a closed bowl).
Once the meat has had enough time to sit, take it out and put it in a baking bag. Top off with water, the remaining soy sauce, oil and white wine. Close the bag and make 1-2 small holes in it. Bake at 360°F (180 °C) for at least 1 hour 10 min. depending on the oven - sometimes it can take 1 hour 30 min.
You'll know when the meat is ready once it gains a nice darkened color. Take it out of the oven and carefully tear the bag open, so pieces of it don't stick to the meat or sauce.
Dilute the remaining sauce in the baking bag with another 1 tbsp soy sauce, 2-3 tbsp water, 2-3 tbsp white wine and 1 tbsp flour. Stir well to get rid of any lumps and put it in a pan or small pot on the stove for 2-3 min. to thicken.
When serving, pour this sauce over the meat to make it even juicier.