Bring milk and honey to the boil, let it cool down for about 10 minutes. Mix the eggs with the honey milk and beat with 1/2 teaspoon salt and sugar over a hot water bath until the mixture becomes thick and creamy.
Leave to cool over a cold water bath, stirring frequently. Stir orange zest into the egg mixture.
Finely puree the selected blackberries with a hand blender. Whip cream until stiff. Line a casserole dish (approx. 18 x 26 cm; 1.3 litres capacity) with parchment paper. Fold the cream into the cooled egg mixture and pour into the casserole dish.
Spread blackberry puree in patches on top and swirl with a spoon. Cover with foil and place in the freezer for 8-10 hours.