Method

• 1.
  ​​To make the crust, preheat oven to 180°C/160°C fan-forced. In a medium bowl, combine the flour, cocoa powder, icing sugar and 1/2 tsp fine salt. Drizzle in melted butter and mix until well combined; it’ll have a texture sort of like Play-Doh.
• 2.
  Press this into the bottom and up the side of a 23cm tart tin with a removable base – or you can use a 23cm pie dish or springform tin. Use a measuring cup or your hands to flatten the crust and make sure it’s all packed and even.
• 3.
  Bake for 15-20 minutes, until the crust is completely cooked through and gone from dark brown and shiny to a lighter dark brown and matte. It can be difficult to tell when this is done, because it’s already brown. Test by pressing the centre: it should be firm and opaque, not squishy or greasy-looking. Remove from the oven and let cool completely.
• 4.
  To make the filling, in a heatproof medium bowl, combine the dark and milk chocolate and a pinch of fine salt. Set aside.
• 5.
  In a small saucepan, heat the cream and honey over medium heat. Once it starts to simmer, remove from heat (do not let it boil) and pour over the chocolate. Let it sit for a minute to melt the chocolate, then, using a spatula, mix until well blended and no pieces of chocolate remain. (You can whisk, but be cautious of air bubbles.)
• 6.
  Stir in the sour cream and mix until thick, glossy and emulsified. Immediately pour filling into cooled crust and smooth the top. Sprinkle with sea salt flakes and refrigerate for at least 1 hour before slicing.