Soak Mu-Err mushrooms in warm water for 15 minutes, then drain and cut into coarse pieces. Remove the skin from the carrots, halve and cut into small strips. Rinse and drain sprouts. Remove ginger from peel and grate finely. Heat oil in a non-stick frying pan and roast pork mince in it for 8 min over medium heat, roughly chopping. Mix sprouts, carrots, mushrooms, minced pork, curry paste, black bean sauce and ginger in a baking bowl, season with salt.
2. lay sheets of dough together on the surface, lightly brush the top halves of the dough with beaten egg white, form 1 tbsp of filling on each of the bottom halves. Fold side edges of dough inward over filling. Roll up dough sheets tightly from bottom to top. Do the same with the remaining dough sheets. Place rolls one at a time on surface and rest for 10 minutes. Finish spring rolls at 170 °C in a deep fryer with hot oil in 2 portions for 4-5 min. Remove rolls and drain on kitchen roll.
For the yogurt dip, peel, halve, seed and finely dice the cucumber. Pluck cilantro leaves from stems and chop finely. Mix mirin, cucumber cubes, yogurt with liquid and cilantro leaves in a baking bowl. Arrange 4 spring rolls on plates and serve warm with the yogurt dip.
Tip: The higher the fat content in the yogurt, the more aromatic and creamy it will be.