Line 4 tart tins or ramekins with nonstick baking paper. Beat the egg whites until they form stiff peaks, then beat in the sugar, a spoonful at a time, making sure the sugar is incorporated between additions.
Fold in the cornflour, vinegar and vanilla extract.
Spoon the mixture into the tart tins or ramekins and cook in a preheated oven, 120°C (250°F), Gas Mark ½, for 2½ hours.
Place the strawberries in an ovenproof dish and bake with the meringues for the last hour of the cooking time.
Spoon the strawberries and any cooking juices over the meringues to serve.