Make cheesecake according to package directions.
Place the thawed strawberries (or raspberries) and sugar in a food processor or blender and process until smooth (or use an immersion blender). It will be about 1 cup of strawberry sauce.
Place the sauce in a medium sized saucepan and heat until warm.
Meanwhile, in a small cup, sprinkle the gelatin over the cold water and let stand 2-3 minutes, or until the gelatin has become soft and spongy.
Add the gelatin to the warm strawberry sauce and heat over low heat, stirring constantly, until the gelatin has dissolved.
Remove from heat and let the sauce cool to room temperature. As it cools, skim off any foam that may formed.
Then slowly pour the strawberry sauce over the top of the cheesecake. A good technique is to hold a spoon close to the filling and then pour into that. It can gently run from the spoon onto the filling.
Cover and place in the refrigerator for several hours, preferably overnight, before serving.
Garnish with fruit and a piece decorative chocolate.