First, toast the marshmallows. You can do this by putting them on a sheet pan and broiling in your oven until browned and toasty. They will burn quickly though, so don’t take your eye off them! Alternatively, a small kitchen torch will toast them as well — just put them in a glass bowl and torch.
Line a small baking sheet with parchment and add the torched marshmallows and broken graham crackers.
Put the chocolate and coconut oil in a microwave safe bowl and microwave on high heat, stirring every 20 seconds or so until smooth.
When melted, pour over the marshmallows and graham crackers. Sprinkle with sea salt if using.
Refrigerate until hard, remove from pan, and break into pieces.