1. Heat oven to 350 degrees. In a small saucepan, melt 5 tablespoons butter. In a medium bowl, combine graham-cracker crumbs and 1/4 cup sugar. Stir in melted butter until crumbs are moist. Pour mixture into a 9-inch springform pan; press firmly, forming a 1/2-inch crust up sides of pan. Bake until set, 12 to 15 minutes. Transfer to a wire rack.

2. Reduce temperature to 275 degrees. In the bowl of an electric mixer fitted with the paddle attachment, beat cream cheese until smooth. Slowly add remaining cup sugar. Scrape in vanilla seeds; reserve pod for another use. Beat until well combined, about 3 minutes.

3. Drizzle in eggs, one at a time, stopping occasionally to scrape down bowl. Beat in sour cream and salt. Pour batter into crust.

4. Bake cheesecake until sides have set but center appears soft, about 1 hour 45 minutes. Transfer pan to a wire rack to cool. Run a paring knife around the outside of crust, loosening it from pan. When cool, cover tightly with plastic; let set at least 4 hours or overnight.

5. To serve, place chocolate, remaining 2 tablespoons butter, and cream in the top of a double boiler or a heat-proof bowl set over a pan of gently simmering water. Stir occasionally until melted. Remove from heat; let cool slightly. Pour chocolate glaze over cheesecake; spread into a circle, leaving a 1/2-inch border. Chill just until chocolate has set, about 10 minutes.