Prepare the base by blending the biscuits and adding the melted butter. Line a 18/20 cm mould and spread on the bottom. Place in the fridge.
Cook the raspberries with the brown sugar and 3 tablespoons of water until you obtain a puree that you then pass through a sieve to remove the seeds.
Soak the gelatine in cold water for at least 10 minutes.
Whip the fresh cream.
Mix the Skyr with the Greek yogurt and sugar. Add the whipped cream with gentle movements and divide the mixture into two parts.
Heat the milk and dissolve half of the well-squeezed gelatine, stirring. Once it has cooled, add it to half of the cream. Pour it onto the cake base and place in the freezer to speed up cooling/solidification.
Heat the sieved raspberry puree and dissolve the other half of the well-squeezed gelatine. Incorporate it into the remaining half of the cream.
Pour onto the white part of the cake that was in the freezer. Decorate as desired (optional) with other fresh fruit and place in the refrigerator until consumption.