Preheat the oven to 210 ° C. Line a baking tray with baking paper and spray with nonstick spray.
1 For the choux pastry: Sift the flour and cocoa together on the baking paper. 2 Mix the milk, butter, sugar and salt in a saucepan and melt over medium heat until the sugar is dissolved. Remove from the heat and add the flour mixture at once. Stir with a wooden spoon until the flour is mixed. 3 Put the pan back on medium to low heat and cook for about 1 minute until the dough pulls away from the sides. Stir constantly. Make sure the dough is cooked thoroughly. The process helps to get rid of excess moisture so that the fritters are crispy. 4 Mix the dough in an electric mixer until slightly cooled. Add the eggs one by one and mix well. Spoon into a piping bag fitted with a 1cm round nozzle. 5 Use the nozzled to form a bold V shapes on the prepared baking tray (it forms the hearts when it bakes) and put in the oven. Reduce the temperature to 200 ° C and bake for 10 minutes. Reduce the temperature to 180 ° C and bake for another 8 minutes. Let cool slightly on a cooling rack. 6 Cut the hearts open and arrange with the cut sides down, on the wire rack. Switch off the oven and put the rack in the oven to cool the hearts and to allow to dry out further (about 1 hour). 7 For the topping: Melt the chocolate and mix carefully with the caramel. Spread the tops of the cooled hearts. Smooth with a hot knife. 8 For the Chantilly cream: Whip the cream, icing sugar and vanilla until it forms stiff peaks. Spoon the cream on the bottom of the Eclair-hearts - add enough so that it is slightly protruding when you close the hearts. Put the tops back on every heart.