Finely chop the chocolate and transfer chopped chocolate to a glass or metal mixing bowl. In a small saucepan, heat the cream over medium heat until it starts to bubble on the sides but isn’t a full boil. Remove the cream from the heat, then pour the cream over the chopped chocolate and let it sit for 8 minutes. Whisk the cream and chocolate until fully combined. Set aside to cool. Once cooled, put about 1-2 Tablespoons in each ramekin (or more if desired) in an even layer and refrigerate the ramekins while you make the panna cotta. Chilling the ganache will result in two distinct layers of chocolate and panna cotta, rather than these combining.

Add the gelatin to the whole milk in a medium saucepan and let the gelatin mixture sit at room temperature for 5-10 minutes until the gelatin begins to bloom.

Place the saucepan over low heat and start whisking the milk and gelatin until the gelatin dissolves completely. This takes just a few minutes. Add the sugar, salt, and instant expresso powder and continue whisking until all solids are dissolved keeping the liquid on low heat. This takes about 3 more minutes.

Whisk in the cream and vanilla to the warm milk mixture and whisk for 30 seconds on the stovetop. Remove from the heat and carefully pour the panna cotta mixture over the chilled ganache in your ramekins, then return them to the refrigerator for two hours. After two hours, cover each ramekin with plastic wrap or cling film and leave refrigerated for at least 1 more hour or up to 3 days before serving.