In a large glass bowl mix the sugar, egg yolks and vanilla essence together. Bring the Carnation light evaporated to the boil and pour over the egg mixture whilst whisking. Place the custard over a saucepan of boiling water and stir until thickened.
Slice the rhubarb about 2 cm thick. Pour the caster sugar and water into a shallow pan. Bring to the boil without stirring until it reaches soft ball stage then add the rhubarb and cook for 2 minutes.
Sieve the flour into a large bowl whisk in the eggs, oil and milk until smooth. Cover and leave to rest for 2 hours.
Pour a little oil into a hot non-stick pan, pour in enough batter to cover the bottom of the pan. Cook for 1 minute, flip and cook for another minute until golden and cooked. Transfer to a plate and cover to keep warm.
Fill the pancakes with the rhubarb and drizzle over the syrup then cover with custard.
Recipe courtesy of Carnation