In a small bowl, mix the warm water, plant milk, and sugar together. Sprinkle the yeast over the top and let it sit for 5–10 minutes until it becomes frothy.
In the bowl of a stand mixer fitted with a dough hook, combine the flours and sea salt. Alternatively, use a large bowl if mixing by hand.
Once the yeast mixture is frothy, add it to the dry ingredients in the stand mixer with the melted butter and knead on medium speed for about 5–7 minutes. Alternatively, mix by hand using a wooden spoon or spatula until a very wet dough forms.
Transfer the dough to a lightly greased bowl, cover with a clean kitchen towel or plastic wrap, and let it rise in a warm place for about 1 to 1.5 hours, or until doubled in size.
