Put 3 – 4 leaves of gelatine in a small bowl of cold water and let soften – about 5 minutes. Pour 450 ml double cream, 200 ml whole milk,
100 g white caster sugar and a tsp vanilla extract into a saucepan and heat gently until hot, but not boiling. Remove the gelatine leaves
from the water and squeeze out any excess liquid, then add to the hot cream, one by one so they don’t stick, and stir until dissolved.
Pour into 6 ramekin dishes – swill out with cold water before filling, and this should make it easier to unmould. Chill for several hours
in the refrigerator, to set. Meanwhile, make the stewed rhubarb: cut rhubarb into 3 – 4 cm lengths and place in an oven-proof dish.
Sprinkle liberally with caster sugar and bake in a 170°C oven for about 20-25 minutes, until just softened, but not falling apart. Let cool.
To serve, run a thin knife around the edge of the ramekin, dip briefly in hot water (don’t submerge it!), then upend the ramekin onto
a serving plate and shake until the panacotta plops out. Serve surrounded with the rhubarb.