Place graham crackers in a food processor and pulse until fine crumbs.
In a bowl, combine graham crackers, cocoa powder, sugar (optional) and butter. Mix with a spatula to combine.
Preheat oven to 325F.
Press mixture to the bottom of a 9x9 -inch square baking dish.
Bake for 8 minutes. Cool completely.
Reduce oven temperature to 290-300 F.
Beat together cream cheese and sugar for 2 minutes. Scrape down the sides and the bottom of the bowl. Add cocoa powder and beat to combine. Add yogurt. Add the melted chocolate and mix for 1 minute.
Add the eggs and beat on low speed, until incorporated.
Pour the cheesecake mixture on top of the cooled crust, smooth the top with a spatula.
Bake the cheesecake for 60-70 minutes, until the top is set, but still a little wiggly. Turn the oven off and leave the cheesecake to cool inside for 30-60 minutes (optional, but prevents cracks).
Remove from the oven and cool completely at room temperature, then refrigerate for at least 2 hours or overnight.
Cut into 9 squares. Drizzle with chocolate ganache (optional). Top each square with a strawberry (optional).