Line an 8"x8" pan with parchment paper so it hangs over the edges slightly. Preheat the oven to 300 degrees Fahrenheit.

For the crust, stir together crushed graham cracker crumbs, crushed pretzels, 3 Tbsp. sugar and melted butter until all of the mixture is moistened. Press it firmly into the bottom of the parchment-lined pan. Bake for 9 to 10 minutes.

While it's baking, prepare the cheesecake layer by first beating softened cream cheese in the bowl of an electric mixer until smooth and no lumps remain. Add sour cream and mix until smooth. Add 3/4 c. sugar, vanilla and egg and mix until smooth, scraping down the sides in between. Add melted semi-sweet chocolate and mix until smooth and creamy.

Pour over baked crust and return to the oven. Bake for approximately 1 hour to 1 hour 15 minutes. Check it often. It will puff up as it bakes. It will still be slightly jiggly when it's done, but not extremely jiggly. The top will form a film.

Allow it to cool completely at room temperature, then cover with foil and place in the fridge to chill overnight. Just before serving, make the ganache by stirring together semi-sweet chocolate chips and heavy cream in a small pan over medium-low heat on the stove top (don't add the full amount of heavy cream at first). Stir constantly as chocolate chips melt. Add more heavy cream to thin out the mixture as necessary, while stirring over the heat, until it's nice and smooth and reaches a drizzling consistency. Let the chocolate on top set, then slice and serve.