1. Date puree: Bring dates and bourbon to a simmer in a small saucepan. Cook until almost all of liquid is absorbed. Remove from heat; cover and let cool. Puree in a food processor until smooth. (You should have 1 cup.)

2. Cake: Preheat oven to 325 degrees. Butter a 9-inch springform pan. Line bottom with parchment; butter parchment. Dust pan with cocoa, tapping out excess.

3. Melt butter and chocolate in a large heatproof bowl set over (not in) a pan of simmering water, whisking until smooth. Remove from heat. Whisk in 2/3 cup date puree. Let cool; whisk in egg yolks, coarse salt, and cinnamon.

4. With a mixer on medium-high speed, whisk egg whites until soft peaks form. Slowly add sugar, beating until stiff peaks form. Fold one-third of whites into chocolate mixture, then fold in remaining whites. Transfer to prepared pan.

5. Bake cake until set (it should be cracking a bit on edges and shiny in center), about 30 minutes. Let cool completely in pan on a wire rack. Run a paring knife around sides; remove from pan.

6. Caramel: Bring sugar and 1/4 cup water to a boil in a small saucepan over medium-high heat, stirring until sugar is dissolved. Let boil, without stirring, until deep golden brown, swirling pan to color evenly, and washing down sides of pan with a wet pastry brush to keep crystals from forming, 10 to 11 minutes. Turn off heat; carefully pour in cream (it will spatter), stirring to combine. Stir in remaining 1/3 cup date puree. Pass caramel through a fine sieve to remove lumps. Let cool until thick but pourable, about 30 minutes.

7. Serving: Pour caramel over cake and spread so it drips over sides. Sprinkle with flaky salt. Cut into wedges with a hot knife, wiping knife between cuts; serve with whipped cream.