First, make the tart crust (Recipe ID: 1422942), and press it into your tart pan.
Make the almond cream. Add to the bowl and mix the ingredients together in order starting with the butter, powdered sugar, whole egg, and then almond flour. Put this into the tart crust, and chill in the refrigerator for about 2 hours.
Bake for about 30 minutes at 170℃. After baking, chill again in the refrigerator.
Mix the ingredients for the Creme Chantilly, beating until soft peaks form.
Cook the purple sweet potato in the microwave or steam in a steamer until soft. Peel, and crumble 140 g of the potato into a bowl.
Add the sugar, milk, and rum, and mix.
Press the mixture through a strainer or potato ricer. Make sure to do this because otherwise, the mixture will get stuck in the tip of the pastry piping bag.
Now you've got your colorful purple sweet potato base.
Add the Creme Chantilly to the potato base from step 8, and mix well to make the Mont Blanc Cream.
Dust just the edges of the tart base with a little powdered sugar, according to your liking. Use a pastry piping bag with a round, 1 cm tip to squeeze the Creme Chantilly onto the tart, leaving a bare 1 cm border around the edges.
First, pipe 4 strips, and then pipe 3 more on top of that (as shown). If you don't have a piping tool, it's actually fine to just use a spoon to pile the cream onto the tart. (There should be some leftover cream which will be used for the border in step 13.)
On top of the Creme Chantilly, pipe out a generous mound of the purple sweet potato cream.
Use the remaining Creme Chantilly to pipe a border around the top of the tart.
Done! To decorate the tart I added some coarsely chopped pumpkin seeds on top of the whipped cream around the edges, and then finished off with a simple decorative pick and a little macaron on top.
I also made a mini size Mont Blanc tart.
Story Behind this Recipe
I found purple sweet potatoes at a highway rest stop store, and I bought them thinking maybe I could try using them in a Mont Blanc tart. The flavor of the purple sweet potatoes was no different from regular sweet potatoes, so I kept the recipe the same as if I'd been using regular sweet potatoes.
- The purple sweet potatoes that I used were the Purple Sweet Road variety grown in Ibaraki Prefecture. - With the amount of Mont Blanc cream that this recipe makes, I was able to make one rectangular tart plus another mini tart. The amount is probably perfect for making one 18 cm tart. - If you use regular sweet potatoes, you'll get a pretty yellow-colored Mont Blanc tart. You can keep all the other ingredients the same.