In a small saucepan, melt cacao butter over low heat. Once fully melted, pour into a large heat-proof mixing bowl or the bowl of a stand mixer fitted with a paddle attachment and let cool to 80 to 90 degrees F (it should no longer feel hot to the touch).Add sugar, salt, baking powder, baking soda, nutmeg and butter. Cream on medium-high speed until mixture is fluffy and nearly white in color, about 3 minutes. Reduce mixer speed to low. Add egg, then vanilla, and continue beating until well combined. Scrape down the sides of the mixing bowl. Mix in flour on low speed until just incorporated, then fold in ruby cacao chips (set aside a few of the chips to place on top if you like).Using a medium cookie scoop, scoop dough into balls (about 2 tablespoons or 36g each). Arrange on a parchment-lined baking sheet and refrigerate for at least 1 hour (you can also freeze the dough balls, then transfer to a zip-top bag for later use).Preheat oven to 325 degrees F.Arrange balls of dough on parchment-lined baking sheets, leaving about 2 inches of space between them. Place a few ruby chips on top if desired. Bake for 13 to 15 minutes or until puffed and just barley starting to brown around the edges; the tops will still be quite pale in color compared to standard cookies. Keep a close eye during the last few minutes as you don’t want to overcook them. I found that darker baking sheets will brown the bottoms much quicker than lighter-colored pans (which is what I recommend using).Let cool on baking sheets for about 5 minutes, then transfer to a wire rack to cool completely. Seal in an airtight container and store at room temperature for up to 4 days.