Line a terrine mould or an old ice-cream tub with cling film.
Bring the sugar and water to the boil and take to 121°C (use a probe thermometer) or soft ball (this is when you remove a teaspoon of the mixture, put it on a plate, allow it to cool then roll in between your fingers – you want a consistency like blue tac).
Meanwhile, whisk egg yolks until light and frothy and mix into the sugar syrup. Whisking all the time until cold.
In a clean bowl whisk the cream to the ribbon stage and fold into the egg yolk mix.
To make the accompanying coulis, boil the rhubarb and raspberries together with a good pinch of sugar until jammy. Pass through a sieve and chill.
Toast a handful of jumbo oats and add to the parfait mix with 2-3 large tablespoons of Scottish heather honey. Combine and pour into the prepared mould. Freeze for 12 hours or overnight and serve with the rhubarb and raspberry coulis and sweet cicely.