Heat the oven to 160°C (140° fan) . Grease and line a 4 cm-deep baking tin, 22 x 33cm with non-stick baking paper.
Beat the sugar and butter in a mixing bowl until thick and creamy.
Gradually beat in the eggs a little at a time. Stir in the milk and vanilla. Gently fold in the flour until incorporated.
Pour the mixture into the tin and smooth the top.
Bake for 25-30 minutes, until golden and springy to the touch. Cool in the tin for 5 minutes, then place on a wire rack to cool completely.
Trim the edges off the cake and cut into 24 squares.
For the icing
Crush the raspberries in a bowl with a fork, stir in 2 tablespoons of boiling water and allow to cool for 5 minutes.
Sieve the raspberry mixture into a bowl, discarding the solids.
Sift the icing sugar into a bowl. Whisk in the raspberry liquid and enough boiling water to form a smooth thick coating icing.
Stir in the food colouring.
Spread the coconut over the base of a tray
Dip 1 cake square at a time into the icing, turning quickly to coat and allowing the excess to drip back into the bowl.
Roll in coconut and place on a wire rack to set.
Stir in the flour gently (don't beat) with a metal spoon. Overworking the mixture results in a leathery sponge.