Step 1

Adjust oven rack to center position and preheat oven to 325°F (163°C).

Step 2

For the Ganache: Place chocolate in a small, heatproof bowl. In a 1-quart stainless steel saucier, heat cream over medium-high heat until it has reached a simmer and started to bubble hard around the edges. Immediately pour hot cream over chocolate and let stand 1 minute. Using a spoon, stir until smooth.

Step 3

Using the same spoon, scrape the ganache into the blind-baked tart shell. Using the back of the spoon, spread ganache in a smooth, even layer that covers the inside bottom of tart shell.

Step 4

Transfer tart shell to a rimmed baking sheet and place in the freezer until ganache is firm, about 10 minutes.

Step 5

Meanwhile, for the Custard: In a blender or spice grinder, process sesame seeds until coarsely powdered, about 5 seconds.

Step 6

In a medium bowl, whisk together powdered sesame seeds, granulated sugar, all-purpose flour, and salt.

Step 7

Add melted butter, honey, tahini paste, and vanilla extract to dry ingredients. Whisk until thoroughly combined.

Step 8

Whisk in egg and egg yolk, followed by sour cream, until mixture is smooth with no visible lumps.

Step 9

Whisk in heavy cream until well combined.

Step 10

Remove baking sheet from freezer and place on a level surface. Pour custard into prepared tart shell, then sprinkle sesame seeds evenly on top. Carefully transfer baking sheet with filled tart shell to oven. Bake until custard is slightly puffed at the edges and the center is just set, about 35 minutes.

Step 11

Set baking sheet with finished tart on a wire rack to cool to room temperature, about 1 hour. Slice and serve.