• Mix the coffee with boiling water in a small bowl or mug and set aside to cool.
• Preheat the oven to 160℃ fan / 180℃ / 356℉.
• Optional step: Tip the walnuts into a baking dish and place in the oven to toast for 5-8 minutes while the oven heats up, until light golden and starting to smell fragrant.
• Set aside to cool.
• Line a 20cm x 10 cm (8 " x 4 ") loaf tin with baking paper.
• Add the butter and brown sugar to a large bowl and beat until light and fluffy - either in a stand mixer or with electric beaters.
• Mix the flour with the pinch salt, baking powder and ground cinnamon.
• Add one egg and mix, then add ⅓ flour. Continue alternating the egg and flour until used up.
• Roughly chop the cooled walnuts then fold into the batter with the cold coffee.
• Gently stir in a tablespoon of milk, adding another ½ tablespoon if the batter doesn't easily drop off the spoon.
• Pour the batter in to the lined tin.
• Place in the preheated oven and bake for 50-55 minutes until a skewer inserted into the middle comes out clean.
• Leave in the tin to cool slightly for 5 minutes, then move to a wire cooling rack and leave to cool completely before icing.

Coffee Buttercream

• When the coffee and walnut cake is completely cold, make the buttercream.
• Mix together the coffee and boiling water - it will be thick. Add a teaspoon of the milk if you need to thin it. Set side to cool.
• Beat the softened butter in a large bowl. Gradually add the sifted icing sugar and beat to combine.
• Pour in the cooled coffee and mix. Add a teaspoon of milk to thin if needed. You want the buttercream to be easily spreadable, but not runny.
• Spoon the buttercream over the top of the cake and use a butter knife or spatula to spread out in an even layer.
• Roughly chop or break the remaining walnuts and scatter over the top.