Soak the gelatin in cold water. Zest the lemon and keep the zest for the oat crunch. Combine the purée with sugar, egg and lemon juice in a saucepan. Heat while stirring constantly until the mixture reaches 85°C. Remove from the heat and add the gelatin. Incorporate the butter gradually. Pass the curd through a sieve and pour it into a piping bag. Cool until serving.
Melt the butter. Chop the chocolate and incorporate it to the butter. Whisk eggs and sugar, add the chocolate mixture and use a hand blender to make it smooth. Add salt to taste. Pour the mixture into a mould, sprinkle cocoa nibs on top and bake 15-20 min at 165°C (depending on the thickness).
Soak the gelatin in cold water. Combine cream, sugar and egg yolks in a saucepan. Scrape the seeds out of the vanilla pod, add them and the pod to the mixture. Heat to 85°C while stirring constantly. Add the gelatin. Strain the mixture and let it cool. Add the sour cream. Pour the cream into a siphon. Load it with 2 gas capsules and keep it cool.
Melt the butter in a pan. Add oat meal, brown sugar and lemon zest. Fry on medium heat until crunchy. Transfer to a tray with paper towel and let it cool. Clean the red currants. Place them in a bowl and mash approximately 1/5 of them. Add the caster sugar and stir carefully until it has dissolved.