Preheat the oven to 190 C / Gas 5. Grease a 900g loaf tin and line with baking parchment.
Combine the instant coffee with the boiling water and mix. Beat the butter and sugar together until light and fluffy then beat in the eggs one at a time beating well after each addition. Add the coffee followed by the flour, baking powder and chocolate chips and beat until smooth, adding the milk gradually. Transfer the mixture to the prepared loaf tin and smooth the top.
Bake in the preheated oven for 60 to 90 minutes until risen and a skewer inserted into the centre comes out clean. Remove from the oven and cool before slicing and serving.