Preheat the oven to 200°C (400°F) and line a baking sheet.
Add the milk, vinegar, and honey to a mixing bowl. Whisk to combine, being sure to mix the honey in.
400 ml (1 ⅔ cups) non-dairy milk, 1 teaspoon apple cider vinegar, 1 tablespoon honey
In a large mixing bowl, add the flour, salt, and baking soda. Whisk or stir to combine.
500 grams (3 ⅓ cups whole spelt flour, 2 teaspoons sea salt, 1 teaspoon baking soda
Pour the milk mixture into the dry ingredients and mix with a wooden spoon or spatula to form a shaggy dough.
Turn the dough out onto a lightly floured work surface and dust the top with more flour. Shape the dough into a ball, then transfer to the baking sheet.
Score the top with an X, cutting about ⅓ of the way into the loaf.
Bake for 35-40 minutes or until golden brown. Cool fully on a wire rack before slicing and serving. You can cut it while still warm but it has a tendency to crumble.
Store at room temperature for up to three days. Soda bread can be frozen but I find it rather dry and crumbly after thawing.
Notes
Don't add more flour: especially if you're using the metric measurements (which I always recommend) resist the urge to add more flour. It is a fairly wet dough but keep in mind that whole grain flour will absorb more water than sifted or white and that the dough needs to be wet in order to have a good oven spring and nice interior texture.
Keep the vinegar: it's necessary in order to react with the baking soda. If you omit the vinegar you will have an unpleasant taste to the loaf and it won't rise as well.
Cool before slicing: for the best texture, cool fully before slicing, at least a couple of hours. It tends to crumble when sliced too soon.