Pre-heat the oven to 180°C/350°F/Gas Mark 5 and grease and line an 8” x 10” cake tin.
Place the 1tbs Original Whirl in a frying pan, add the rhubarb and sauté until it starts to soften (about 5 minutes), drain and set to one side.
In a bowl add the eggs, sugar, 160g Unsalted Whirl, milk, flour and baking powder. Mix well to incorporate all the ingredients then add 3 tablespoons of custard to loosen the mix slightly.
Put the mix into the prepared cake tin make random small wells in the top of the cake and fill with the remaining custard.
Now put the rhubarb over the top of the sponge and custard mix, place in the oven to bake for about 40 minutes until firm and springy to the touch.
Allow to cool in the tin for 5 minutes before transferring to a cooling rack.