Step 1

Preheat oven to 350 degrees. Stir together cookie crumbs, melted butter, and 3 tablespoons sugar in a medium bowl. Press crumb mixture firmly onto bottom and up 1 inch on sides of a 9-inch springform pan. Bake until set, about 10 minutes. Transfer to a wire rack, and let cool. Reduce oven temperature to 300 degrees.

Step 2

Melt chocolate in a medium heatproof bowl set over a pan of simmering water, stirring, about 2 minutes. Let cool.

Step 3

Put cream cheese in the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until fluffy, about 3 minutes. With mixer on low speed, add remaining cup sugar in a slow, steady stream. Add salt; mix until combined. Add sour cream, cocoa, vanilla, and melted chocolate; mix until combined. Add eggs, one at a time, mixing each until just combined (do not overmix). Pour cream cheese filling over crust.

Step 4

Bake until set but still slightly wobbly in center, 50 to 60 minutes. Let cool completely in pan on rack. Refrigerate, uncovered, 6 hours or overnight. Before unmolding, run a knife around edge of cake.