Roasted Rhubarb Chocolate Tart

5 from 1 vote

A decadent rhubarb chocolate tart filled with a layer of roasted rhubarb compote and topped with chocolate ganache

Prep Time45

Cook Time40

Total Time1 10

Course: Dessert

Cuisine: French

Servings:

Calories: 371kcal

Cacao Barry extra brute cocoa powder for dusting on the finished tart before serving
dried rose petals for decorating the tart

Cream together the butter, icing sugar and cocoa powder until smooth and well mixed.
Add the egg yolk and mix it in, then add the flour and salt and mix the dough to form a crumble.
Add the milk and mix it in to bind the dough together.
Shape the dough into a disk and wrap it in plastic wrap. Refrigerate for at least 1 hour or until firm.
Roll out the disk of dough between two pieces of parchment until it is 3 mm thick.
Line a 9-inch removable bottomed tart pan with the dough and work it into the corners and edges. Trim and neaten it up.
Chill the unbaked tart for half an hour or until very, very cold.
Preheat the oven to 350 °F (175 °C) while the tart base chills.
Dock the pastry with a fork to allow steam to escape (make sure to cut all the way through).
Place the tart on a baking sheet and blind bake the tart shell for about 20–25 minutes until the pastry is fully cooked and appears dry (not glossy). Watch for air bubbles forming under the pastry. If this happens, take a fork, a thin pairing knife, or even a cake tester to poke through the pastry, gently pressing it back in place. Once the crust has set, air pockets won't form anymore.
Remove the tart from the oven. Let it cool before unmolding it carefully and placing it on a plate.

Combine the chopped rhubarb and sugar in a small saucepan and heat it over medium–high heat to melt the sugar and soften the rhubarb. When it boils, let the compote boil for several minutes to cook the rhubarb and boil off as much of the water as possible. Set aside to cool.

Heat the cream in a small saucepan until it is steaming hot (just below 80 °C or 175 °F), then pour it over the chopped chocolate.
Wait two minutes for the heat to disperse, then begin to stir it from the middle, out, until you obtain a smooth, silky ganache. Use an electric stick blender to ensure the chocolate is all melted and the mixture well emulsified. (If all else fails, see above for my ganache saving tip in the notes!).

Line the bottom of the baked tart shell with an even layer of the rhubarb compote.
Top with ganache, smoothing it out from edge to edge. Let the tart set in the fridge for a couple of hours.
When you are ready to serve the tart, dust the top with some cocoa powder to make it pretty and decorate with dried rose petals.

This recipe calls for Diamond Crystal fine Kosher salt. If using regular table salt, add half the amount or the recipe may be too salty!
For the dark chocolate, I used Cacao Barry Ocoa 70 % dark chocolate.
When making dark chocolate ganache with a high percentage of cacao and low in sugar, the ganache may separate. This means the fats begin to separate from the creamy chocolate mixture. It just won't look right (might even be lumpy and greasy looking) and when you chill it, you will notice white cocoa butter drops on the surface of the ganache.
- One way to stabilize dark chocolate ganache and prevent separation is to add a little glucose (corn syrup or even honey) to the cream. Heat the cream in this recipe with 15 grams of glucose (or corn syrup or honey) to melt it in. This should help you achieve a more stable ganache that is less prone to separating.
- I like to use a stick blender (hand blender) to combine the cream and chocolate. I find my ganache doesn't break when I use the stick blender.
- Don't overheat the cream - if it's too hot, your ganache may split! Make sure it is under 80 °C before adding it to the chocolate.
- If your ganache splits or breaks, the emulsion of the ganache is broken, but you can fix it before pouring the filling in the tart shell! Add a couple of tablespoons of cold milk at a time (or even water), stir a lot and repeat this until it comes together, et voilà: silky smooth chocolate ganache!