For the cupcakes, mix the instant coffee and boiling water together, set aside to cool fully
Pre-heat your oven to 140C Fan/Gas Mark 3, and line a cupcake tin with cupcake cases
For the cupcake sponge, mix together the baking spread and golden caster sugar, ideally using an electric hand mixer or in a stand mixer with the paddle attachment, for 5 minutes until smooth and fluffy
Add the eggs, the cooled coffee and water mixture, and coffee extract if using, and mix them in well
Gently whisk, or fold in, the self raising flour. Add the chopped walnuts and fold them in
Divide the mixture between the cupcake cases, and bake them for 25-30 minutes or until a thin skewer inserted in the centre of the cupcakes comes out clean. Put them on a rack to cool completely
For the buttercream, mix the instant coffee and boiling water together, set aside to cool fully
Mix the softened butter on it's own for a few minutes. Then add the icing sugar, the cooled coffee and water mixture, milk and, if using, the coffee extract. Mix until smooth. You can do this by hand, but an electric whisk or stand mixer with paddle attachment will provide the best results. If the buttercream is too stiff, you can add a little more milk
Spread or pipe the buttercream on top of the cupcakes
Decorate with the whole and chopped walnuts
Store in an airtight container in a cool place and eat within 3 days