Fill the bottom of a small double-boiler with water. Break chocolate bars into chunks and place in the top of the double boiler. Cover a baking sheet with wax paper.

Stir the chocolate occasionally until it is fully melted. Holding a mango slice by its end, dip it in the chocolate until it is about two-thirds coated in melted chocolate. Place the chocolate-covered mango on the baking sheet. Repeat with remaining mangos. Once all mangos have been dipped, put the baking sheet in the freezer. Once chocolate is firm, remove mangos from the sheet and store in an airtight container.