In a non-stick or heavy bottomed pan, heat milk, cream and sugar on a low flame until the mixture comes to a boil.
In another bowl, add gelatin to 1 teaspoon water and place it on stove. Stir well until all the gelatin dissolves. (You can alternatively melt it in a microwave.)
Add the gelatin mixture to cream-milk mixture and stir well with a whisk until the mixture blends well. Allow it to cool down.
Remove half of the quantity and keep aside.
Take the remaining half quantity, add in the melted dark chocolate and whisk well.
Spoon this panna cotta mixture into glass or bowls and set it in freezer for about 2-3 hours. Set one layer and then add the next layer and freeze again.
Top it with some fresh strawberries and mint leaves and serve it chilled.