Toasting the sesame seeds before making the tahini gives the sauce a far superior flavour. Transfer the toasted sesame seeds to a food processor, then blend until a crumbly paste forms.

Put all the ingredients except the black sesame seeds in a large bowl ... mix the softened butter with the tahini and icing sugar, starting slowly or you'll have a big mess!

If you are not familiar with tahini, it is a paste made from ground sesame seeds ... To remove, simply gently squeeze each bean and the skin will pop off. Place beans into a food processor.