First, make the dark chocolate layer by mixing 6 TBSP coconut oil, 1 1/2 TBSP Gentle Sweet, 1/4 tsp peppermint extract and small pinch of salt in a bowl. I did not need to melt it but if you do, only do it for like 10 seconds. You don't need it warm. Spread it as thin and evenly as possible in an 8x8 square dish lined with wax paper. Place it level in the freezer.
Now make the white peppermint layer. Just like the chocolate layer, mix together 6 TBSP coconut oil, 2 TBSP Gentle Sweet, 1/2 tsp peppermint extract and small pinch of salt. If the chocolate layer is already firm (which shouldn't take more than 15 minutes), add the peppermint layer and sprinkle with peppermint pieces. Return to the freezer at least another 15-20 minutes.
When the bark is firm, remove the whole sheet of wax paper holding the bark, lay out on the table and cut or break into pieces. It will not stay firm at room temperature very long, so store it in the freezer until you are ready to enjoy it!