Cook the apples. Cut the 400 g of peeled, cored apples into chunks. Place in a saucepan with 80 g water and cook over medium heat, covered at first, then uncovered for the final few minutes, until very soft. This takes approximately 15–20 minutes. Make sure the pan does not dry out and the apples do not stick.
Blend until smooth. Blend the cooked apples with any liquid remaining in the saucepan until you have a smooth purée with no chunks.
Bloom the gelatin. Pour the 60 g cold water into a small bowl and sprinkle the 12 g unflavored powdered gelatin over the surface. Let stand for 5–10 minutes to hydrate.
Dissolve the gelatin. If the apple purée has cooled, reheat it until hot but not boiling. Remove from the heat, add the bloomed gelatin, and stir until completely dissolved.
Whip until fluffy. While the mixture is still hot but not boiling, beat with an electric hand mixer fitted with beaters or a stand mixer fitted with a whisk for about 15 minutes. The mixture should become paler, increase in volume, and develop a light, airy texture. Follow your mixer’s instructions for maximum running time and breaks. Do not use a blender for this step.
Transfer to the pan and chill. Spoon the mixture into a pan approximately 20 × 15 × 5 cm (8 × 6 × 2 inches), lined with parchment paper. Smooth the surface and refrigerate for 4–6 hours, or overnight, until set.
Slice and serve. Carefully lift the mixture out of the pan, peel away the parchment paper, and cut into cubes.
