Defrost raspberries at room temperature. Melt butter in a small pot, remove from heat and let it cool down a little. Crumble the biscuits, mix with the butter. Line a square tin (approx. 24 x 24 cm) with baking paper. Add the crumbly mixture and press to a smooth base. Put them in a cool place for about 30 minutes.
Chopping chocolate. Heat condensed milk with vanilla, bring to the boil briefly. Remove from heat, add chocolate and let it melt while stirring occasionally. Pour the mixture onto the crumb base and spread quickly. Chill for about 1 hour.
Puree the raspberries and pass through a sieve. Measure 150 ml puree and fill up to 200 ml with cold water. Pour into a small pot and stir in the gelatine powder well. Leave to swell for about 2 minutes. Sieve the icing sugar into a bowl. Heat the puree while stirring and bring to the boil briefly. Immediately pour into the icing sugar while stirring with the whisks of the hand mixer and whip for approx. 4 minutes to a firm, frothy mass until peaks form.
Pour the mixture immediately onto the fudge and spread quickly. Add the rest of the raspberry puree and spread in waves. Leave to dry for about 1 hour. Remove the fudge from the tin and cut into approx. 36 cubes. Store in an airtight container.