Begin by adding the vinegar to the non-dairy milk. Set aside for 10 minutes. This is your vegan buttermilk.
Place an 8-inch (20cm) cast iron skillet into the oven. Preheat to 400°F (200°C).
Add the cornmeal, flour, baking powder, salt, sugar, and chopped herbs to a large mixing bowl. Mix to combine.
Add the vegan buttermilk and ¼ cup of melted butter to the dry ingredients. Stir to combine. The batter will have the consistency of banana bread.
Cover and set aside to rest for 10-15 minutes for the cornmeal to hydrate.
After resting, take the preheated skillet out of the oven. Add the remaining 2 tablespoons of butter and swirl it to cover the base of the pan.
Add the batter, smoothing the top with the back of a wooden spoon or spatula. Bake for 20-23 minutes, or until golden and the centre springs back lightly when touched.
Cool in the pan for 10 minutes before slicing and serving. Vegan cornbread will keep for a few days in an airtight container, but it's best fresh.