Dulce de leche is sold in the Hispanic aisle of supermarkets, or in Hispanic specialty markets. It is sold in solid 15-ounce blocks, or in cans or bottles in more of a liquid form. You can also find recipes for making your own dulce de leche using sweetened condensed milk.
Combine the cream and sugar in a large bowl and whip until stiff.
Pour the very hot coffee into 6 oversized mugs and divide the dulce de leche among the mugs (1 ounce in each). Stir until completely dissolved and combined. Add 1 tablespoon whiskey to each mug. Top with a heaping tablespoon each whipped cream and grated chocolate.