Prepare a clean, grease-free mixing bowl and food processor (or hand mixer), and preheat the oven to 130°C/Fan. Place the egg whites into the bowl and whisk until stiff. Slowly add sugar to the bowl while continuing to whisk. Now add the vinegar and baking powder until stiff and creamy. Warm the caramel to a liquid consistency, drizzle a little into the meringue mixture and swirl in gently. Spoon the mixture into small mounds on a baking paper-lined tray. Reduce the oven temperature to 100°C, and bake the meringues for 110 minutes.
Heat the water, salt, vanilla and butter in a small pan. Remove from heat just before it begins to boil, add all the flour at once and stir until the mixture is smooth. Return to heat and continue to stir for a few minutes until the mixture forms a ball. Transfer the mixture to a bowl and leave to cool until it is just slightly warm to the touch. Now stir in the eggs one by one. Spoon the mixture onto a baking paper-lined tray in the form of a ring, leaving very little space between scoops. Brush a little water over the ring and bake at 190°C/Fan for approx. 30 minutes. When the pastry is cooked through, open the oven door slightly and use the handle of a wooden spoon to keep it ajar. Remove from the oven after 20 minutes and leave to cool. Now cut the ring in half horizontally, and place the lower half on a serving dish.
Wash, core, halve and slice the Pinova apples. Place in a small pan with a little lemon juice and caramel and cook at a low temperature for approx. 10 minutes until tender but firm, stirring occasionally. Leave to cool.
Whip all ingredients except the stabiliser until the cream is smooth and thick. Now add the stabiliser and combine well. Fill the ring with the cream, then crumble the meringue and sprinkle on top. Arrange the apple slices over the mascarpone cream, place the upper part of the pastry ring on top and dust with icing sugar.
Never open the oven door while the pastry is baking or the choux pastry will collapse!