Coffee and Walnut Cupcakes

Name: Coffee and Walnut Cupcakes
Prep time: 20 min
Cook time: 20 min
Total time: 40 min
Cuisine: American, British
Ingredients: 200 g Unsalted butter (at room temperature); 200 g Caster sugar; 4 Medium Eggs; 200 g Self-raising flour; 1 Teaspoon Baking powder; 2 Tablespoons Instant coffee; 1 Tablespoon Boiling water (to dissolve the coffee); 50 g Walnuts (Roughly chopped ); 2 Teaspoons Instant coffee; 1 Teaspoon Boiling water (to dissolve the coffee); 200 g Unsalted butter; 400 g Icing sugar (sifted); 1 Walnut halves ( optional to decorate ); Coffee beans ( optional to decorate )