In a large bowl, whisk together the flour, cornmeal, sugar, baking powder, salt, and pepper until thoroughly blended. Cut the cold margarine into 1/2-inch pieces before tossing them in as well, mixing to coat with the dry goods. Use a pastry cutter or two forks to cut the margarine in, stirring and mashing so that you achieve a coarse, crumbly consistency. You don’t want the margarine to become completely incorporated, but there should be no pieces remaining that are any larger than petite peas.
Shake the coconut milk well before opening to ensure that it’s properly mixed. Pour it into the bowl and stir with a wide spatula, just until the mixture comes together. Never mind an errant lump or two; they’ll bake out just fine!
Once you have a slightly shaggy, sticky dough, transfer it to a well-floured surface and pat it into a rough rectangle about 1-inch thick. Take a very sharp knife and cut it in half lengthwise, and then into either thirds or fourths crosswise, depending on how large you want your biscuits. This will result in 6 or 8 neat little squares. Gently transfer the cut biscuits to your prepared sheet pan, reshaping slightly if necessary, and brush the tops lightly with additional coconut milk to promote browning.
Bake for 18 – 22 minutes until golden brown all over. Let cool for at least 5 minutes before digging in. To save the biscuits for later, let cool completely and store in an air-tight container at room temperature. The finished biscuits will keep for up to 4 days.