For the cakes
Cook the potato in a large saucepan of salted, boiling water until just tender to the tip of a knife, about 10 minutes.
Drain well and leave to cool briefly before mashing in a bowl with the olive oil, nutritional yeast, cornflour, and salt.
Preheat the oven to 190°C (170° fan) | gas 5.
Grease the holes of a 12-hole cupcake tin with some olive oil.
Divide the potato mixture between the holes of the tin, pressing into the base and sides of each hole to make a cup.
Bake for 20-30 minutes until golden and set.
Remove the tin to a wire rack to cool.
For the filling
Heat the olive oil in a large sauté pan set over a moderate heat.
Add most of the cabbage (reserving some for a garnish) and the carrot to the pan with a pinch of salt.
Sauté for 4-5 minutes until softened, stirring frequently.
Stir in the soy sauce, rice wine vinegar, and pepper to taste; add more soy sauce or rice wine vinegar as desired.
Spoon the filling into the potato cups and top with the reserved cabbage.
Garnish with a sprinkle of chopped chervil and some more freshly ground black pepper before serving.