Place pork fillets in a shallow glass dish. In a small bowl, whisk together soy sauce, hoisin sauce, sherry, black bean sauce, ginger, sugar, garlic, sesame oil and five-spice powder. Pour marinade over pork, and turn to coat. Cover, and refrigerate for at least 2 hours or up to 24 hours.
2.
Preheat oven to 190 C / Gas mark 5. Remove fillets from refrigerator while the oven preheats.
3.
Bake pork in preheated oven for 30 to 35 minutes, or to desired doneness. Let stand for 10 minutes, and then slice diagonally into thin slices.
I had to adapt slightly due to the ingredients I had, ie Sharwoods yellow bean and chilli sauce instead of Black bean sauce,and Hoisin and spring onion sauce instead of plain hoisin sauce, and I added 1 tsp 5 spice powder not a pinch, but it was absolutely delicious.I used these quantities for 1lb fillet not 3, but there probably would just have been enough without basting for 3. Will definitely use again.