For the dough
- Add water, butter, and salt to a saucepan, then bring to a boil, stirring constantly. Add flour and cinnamon to the saucepan, and mix in thoroughly with a wooden spoon. Remove from heat and let cool to room temperature, then beat eggs into mixture one at a time. Let sit for 20 minutes.
- Once cool, transfer to a pastry bag that has a star-shaped tip.
- Take a large piece of parchment paper and cut into 7.5 x 7.5 centimeter squares. Using your pastry bag, create a ring of dough on each square of paper.
- Pour vegetable oil into a pot with high sides until it reaches several inches high. Heat the oil to 375 F (190 C), then carefully lower two to three pieces of paper with rings attached into oil, batter side down, making sure to keep your fingers away from the oil. The parchment paper will separate from the ring once it hits the oil, at which point you should remove the parchment using metal tongs. Fry the rings until golden-brown, turning once, then remove using a slotted spoon to a paper-towel lined plate. Repeat until all rings are fried, then set aside to cool.
- Once pastry rings have cooled, sprinkle with icing sugar.
For the sour cherry mascarpone whipped cream
- Add whipping cream to a chilled bowl, then beat with a hand blender or whisk until thick. Add mascarpone and sour cherry syrup to cream and continue to whip until thick peaks form. Add sugar as you whip until just combined.
- Fill another pastry bag with a round tip with the sour cherry mascarpone whipped cream, then top the hole of each ring with a mound of whipped cream. To finish, top the cream with a sour cherry, and drizzle over a little of the sour cherry syrup.