Butter a 9-inch round springform pan and line the bottom with parchment paper. I do this by trapping the parchment between the bottom and the sides of the pan, it makes for easy movement later on. Preheat the oven to 350°F.

In the bowl of a stand mixer fitted with the paddle attachment, combine butter, white sugar and 1/4 cup brown sugar. Beat at medium speed until light and creamy. Scrape down the sides of the bowl once or twice during the mixing.

Crack in the egg and add the vanilla. Beat again until very well combined. Scrape down the sides of the mixing bowl.

Sift the flour and baking soda into a separate bowl. Whisk in the salt and nutmeg. Measure out 2 tablespoons of this flour mixture and toss with the rhubarb and carrots in another bowl.

With the mixer on Low, add the dry ingredients to the creamed butter in three parts, alternating the buttermilk with the flour, finishing with the flour. Mix well with each addition.

Add the rhubarb & carrots to the cake batter and gently stir to combine. Scrape the batter into the prepared cake pan and smooth the top.

Mix together the remaining 1/4 cup of brown sugar with the cinnamon. Sprinkle over the cake batter. Run a butter knife through the cake, making a few figure eights to swirl the cinnamon into the batter.

Place the cake on a middle rack in the centre of the oven and bake until a toothpick inserted in the middle comes out clean. About 1 hour or 1 hour and 10 minutes. It will get quite dark on the top.

Cool the cake for 10 minutes on a wire rack, then loosen around the edges and remove the ring. When cool, frost generously with Whipped Mascarpone Frosting (recipe below), then slice and serve.

In the bowl of a stand mixer fitted with the whisk, combine all of the ingredients.

Whip on high until the cream holds soft peak. Do not walk away; the cream whips very fast! Do not over mix as the frosting may become grainy.

Use immediately for frosting Rhubarb Carrot Cake. Decorate with the Rhubarb Curls

Combine the sugar and water in a small pot. Warm over medium heat until the sugar has completely dissolved. Set aside to cool. Preheat oven to 200F

Wash and trim the rhubarb, cut in half cross wise and then lengthwise. This will help stabilize the rhubarb as you run the peeler over them. Firmly press down with a vegetable peeler starting at a cut edge and grabbing that edge in the blade. Peel firmly into long, even strips. Put the cooled sugar syrup in a small bowl and submerge the rhubarb strips one by one and then transferring them to a parchment lined baking sheet.

Arrange the rhubarb strips in a single layer, not touching, smoothing them so they lie flat.

Bake until the strips are dried out and fairly crisp – they should be dry and not really tacky to the touch. If they are overcooked, they will crack and break when you try to curl them. Start checking after 35 minutes, depending on your oven. Some slices will be ready before the others, depending on the thickness of the slice and how evenly your oven heats.

After you have removed them from the oven work quickly, otherwise they will set. Curl round various implements – wooden spoons, chopsticks, straws (you need quite a lot) and leave to set for 10 minutes. Make sure you choose implements that don't have an end that is larger than the curls, or else you won't be able to slide them off. If the rhubarb doesn't hold its shape, it needs a little longer in the oven.

Once they are keeping their shape, transfer them to a paper lined plate and use. Extra ones can be stored in a sealed container. They are great on oatmeal or yogurt the next day!