Preheat oven to 170 degrees celsius (fan-forced). Grease and line the base and sides of a loaf tin (approximately 13cm x 24cm).
Using hand-held beaters or a stand mixer, beat the softened butter, brown sugar and caster sugar until pale and creamy. If using a Thermomix: Place the butter, brown sugar and caster sugar into the Thermomix bowl and and mix for 15 seconds, Speed 5. Scrape down the sides.
Add the eggs (one at a time) and the vanilla extract and beat until combined.If using a Thermomix: Add the eggs and vanilla extract and mix for 5 seconds, Speed 6.
Pour in the dissolved coffee and beat to combine (don't worry if the mixture curdles).
Sift the plain flour, baking powder and salt into a separate bowl.Alternate beating through the milk and the sifted plain flour/baking powder and salt. Stir through the chopped walnuts.If using a Thermomix: Add the milk and mix for 5 seconds, Speed 4. Then add the plain flour, baking powder and a pinch of salt. Mix for 5 seconds, Speed 6. Scrape and repeat for a further 5 seconds (or until combined). Stir the walnuts through with the spatula.
Pour into the prepared loaf tin and cook for 1 hour, or until a skewer inserted into the middle comes out clean (if the loaf is browning too quickly, add a sheet of foil loosely over the top). Allow to cool in the pan for 10 minutes before turning out onto a wire rack to cool completely.
Notes
RECIPE NOTES & TIPS:
Check expiry dates on your walnuts - you want fresh crunchy walnuts for the best loaf.
Omit the walnuts - if you want a nut-free loaf, although I think they add a welcome flavour and crunch to the texture.
If your coffee walnut loaf is over-browning on top (it happens... all ovens are so different), simply place a sheet of foil loosely over the top and continue baking.
Test to see if it's cooked - insert a skewer into the middle of the loaf near the end of baking time. If it comes out clean or with just a few crumbs, it's cooked. If not, continue baking for a few more minutes and test again.
Store your loaf at room temperature in an airtight container for 4-5 days.
Freezing - you can freeze the whole loaf, or as slices. Wrap loaf or slices in foil or plastic wrap and freeze in an airtight container for up to 3 months. Defrost at room temperature before serving.