Melt butter + brown sugar in a medium saucepan over medium heat. Add the cream and bring the mixture to a boil, whisking constantly for 1 minute. Take off of the heat and whisk in the ground coffee, vanilla and salt. Let cool for 5 minutes and then add in the powdered sugar until it comes together in a thick paste. Stir in the crushed burnt sugar*. Chill in an airtight container for several hours or overnight. If you store it overnight, you may need to leave it at room temperature for a bit to become more easily scoopable (scoopable is a word, right?).
Cover a baking sheet with parchment paper. Using a cookie scoop**, scrape up 1 tablespoon (14 g) of the brown sugar mixture. Scrape the bottom of the scoop against the side of the dish so that it’s flat and release the truffle onto the prepared baking sheet. Place the truffles in the freezer for several hours or until frozen and firm.
For the truffle coating, in a medium, heat-safe bowl, add the chocolate and set over a medium saucepan of simmering water. Do not let the bowl touch the water or let the water come to a boil. Stir frequently until barely melted and not quite smooth. Set on top of a hand towel and stir until all of the lumps are gone. Set aside, stirring frequently while it cools.
Set some parchment paper underneath a cooling rack.
Using a dipping or regular fork, dip the frozen truffles into the chocolate coating. Tap the fork on the side of the bowl, letting the excess chocolate fall back into the bowl. Place the truffle on the cooling rack. Let the truffles set for 1 hour. Either garnish with the crushed burnt sugar or the gold leaf (as detailed in the notes section). Transfer to an airtight container (lined in parchment with parchment separating each layer of truffles) to store in the fridge until ready to serve for up to several weeks.