Toss the bananas in a little lemon juice and mash on a plate with a fork. Add the ginger and yogurt and mix together. Spoon one-third of the mixture into the bases of 4 small dessert glasses.
Sprinkle 1 teaspoon of the sugar over each dessert. Spoon half of the remaining banana mixture on top, then repeat with a second layer of sugar. Complete the layers with the remaining banana mixture and decorate with a little extra ginger, cut into slightly larger pieces.
Leave the puddings to stand for 10–15 minutes for the sugar to dissolve and form a syrupy layer between the layers of banana yogurt. Serve with dainty biscuits, if liked.