for the crust:
1 & 1/2 cups graham cracker crumbs
1/3 c. dutch-process cocoa (such as Hershey's Special Dark)
1/3 c. sugar
1/3 c. salted butter, melted

for the cheesecake:
3 (8 oz.) packages cream cheese, softened
1 (14 oz.) can sweetened condensed milk
3 eggs, room temperature
2 teaspoons vanilla extract
1 cup mini chocolate chips, divided
1 teaspoon flour

for the sauce:
1 cup water
1/3 cup sugar
1/3 cup light corn syrup
1/4 cup dutch-process cocoa (such as Hershey's Special Dark)
2 ounces unsweetened chocolate, finely chopped
3 ounces bittersweet chocolate, finely chopped
3 ounces dark chocolate, finely chopped