This decadent rhubarb chocolate tart is made with a chocolate cookie crust and has a layer of roasted rhubarb compote tucked beneath the dark chocolate ganache.
I have been patiently holding on to this recipe from a Donna Hay magazine for years (it's from issue 58) and waiting for rhubarb season to begin. This tart is sinfully good and a great change from the usual rhubarb recipes. Of course, if you don't love rhubarb, just make the tart with plain, or layer some homemade salted caramel on the bottom before topping with ganache... and if you would prefer milk chocolate, try this raspberry chocolate tart which is filled with a milk chocolate ganache and topped with fresh raspberries before serving.
Like with most chocolate desserts on this site, remember to please use good quality chocolate for this recipe because ganache is 50 % chocolate. Get the best type of chocolate you can with a fairly high percentage of cacao that isn't overly sweet and that will make the ganache so much better. I used a 70 % dark chocolate from Cacao Barry. Ocoa chocolate works great in this recipe, for example!
Tips for perfect chocolate ganache:
- Use one type of chocolate to make ganache: What I discovered from making this tart is that, though it was very convenient to use a mixture of dark chocolates to use up the odds and ends in your cupboards, the combination of chocolates makes it more difficult to achieve a perfect ganache and the ganache may split or break if you use a mixture of chocolates.
- If ganache breaks, you can fix it: if you make your ganache incorrectly, you will find that as you stir it, the fats begin to separate from the creamy chocolate mixture and it just won't look right. If this happens, the emulsion of the ganache is broken, but you can fix it! Simply add a couple tablespoons of cold milk (or even water), stir, et voilà: silky smooth chocolate ganache. It works. Trust me. This tart is proof!
- A 1:1 ganache is the easiest ganache to make: if this is your first ganache, make it a 50/50 ganache that is half cream, half dark chocolate, by weight. You will have an easier time melting the chocolate and emulsifying the mixture than a ganache with a higher ratio of chocolate.
For this recipe, I roasted a pan of rhubarb with sugar to make a soft rhubarb compote. You want the rhubarb to "fall apart" into a compote that will fill the bottom of the tart shell snuggly. This is different than the roasted rhubarb that was roasted in a poaching liquid in the oven just until soft, but not falling apart.
Of course, if this rhubarb tart seems like a lot of work, but you still want to bake with rhubarb, you can always make strawberry rhubarb crumble muffins, rhubarb jam, or even a mini strawberry rhubarb crumbles or bluebarb (blueberry rhubarb) crisp.
The chocolate cookie crust for this rhubarb chocolate tart is similar to a pâte sucrée but where part of the flour is replaced with cocoa powder. It's baked in a tart pan with a removable bottom. To unmold the crust, check out my tips for how to remove a tart from a tart pan.
Roasted rhubarb chocolate tart
- 185 grams (1½ cups) all-purpose flour
- 80 grams (⅔ cup) icing sugar
- 25 grams (⅓ cup) Cacao Barry extra brute cocoa powder
- 115 grams (½ cup) unsalted butter cut into small pieces
- 3 (3 ) large egg yolks
- 30 mL (2 tbsp) cold water optional, depending on texture of dough
- 225 grams (½ lb) fresh rhubarb washed and trimmed, and cut into 10 cm lengths
- 30 mL (2 tbsp) granulated sugar
- 15 mL (1 tbsp) rose water
Dark chocolate ganache
- 300 grams (⅔ lb) Cacao Barry Ocoa 70% dark chocolate chopped
- 250 mL (1 cup) whipping cream (35 % fat)
- Cacao Barry extra brute cocoa powder
To make the chocolate dough
- Sift the flour, cocoa powder, and icing sugar into a large bowl.
- Add the cold butter and work it into the flour mixture by rubbing your palms together through the mixture until the mixture resembles fine breadcrumbs.
- Make a well in the center and add the yolks. Work the yolks into the dough with a fork or even your fingers.
- If the dough is slightly dry, add a spoonful or so of cold water until the desired texture is obtained.
- Form the dough into a disk and wrap it in plastic wrap. Refrigerate for at least 1 hour or until firm.
- Preheat the oven to 350°F.
- 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.
- Freeze the unbaked tart for half an hour or until very, very cold.
- Dock the pastry with a fork and with a 6 mm piping tip, cut out a whole in the center of the tart to allow steam to escape (make sure to cut all the way through and remove the piece).
- Place the tart on a baking sheet and blind bake the tart for about 15–20 minutes until the pastry is fully cooked and appears dry (not glossy).
- Remove the tart from the oven. If there are any bumps of air under the surface of the tart shell, press down very gently with a clothed hand (beware of steam) to release the steam. Let cool before unmolding it carefully and placing it on a plate.
To roast the rhubarb
- Toss rhubarb with the sugar and rosewater and bake it in a glass ovenproof dish until the rhubarb is tender (about 20 minutes). Let cool completely before using.
To make the chocolate ganache
- Heat the cream in a small saucepan and when it is steamy, pour it over the chopped chocolate.
- Wait a minute, then begin to stir it from the middle, out, until you obtain a smooth, silky ganache. (if all else fails, see above for my ganache saving tip!). Let the ganache thicken slightly before using.
To assemble the tart
- Line the bottom of the baked tart shell with the rhubarb.
- Top with ganache, and let the tart set in the fridge for a couple of hours.
- When you are ready to serve the tart, sprinkle the top with some cocoa powder to make it pretty.