Measure coconut oil while firm, transfer into a bowl and place in the fridge to chill and become very firm
Preheat the oven to 190C or 375F
Measure the milk and add vinegar. Leave it to stand to get a vegan "buttermilk"
Sift flours, salt and baking soda into a bowl. Add sugar and mix well.
Cut the chilled coconut oil using the knife in very small pieces and add into the bowl with dry ingredients
Rub the oil into the dry ingredients using your fingers to crumble it together, same as you do when you make pie dough
Then add walnuts and "buttermilk"
Using a spatula or a spoon mix until the ingredients have been incorporated into a wet dough
Transfer the dough onto a very well floured surface
Roll it and flip adding the flour until it is realatively firm and no longer too wet to handle. It will still be a little wet inside
Shape it into a loaf, transfer onto baking pan lined with lightly floured parchment paper
Make a cross on the dough using a sharp knife - this is done to ensure more even baking
Bake for 30 minutes. When done, the loaf should be nice and golden brown, and when pierced with a toothpick, should come out dry