Plum Mousse Pie

Instructions

1. Instructions:
2. Make ahead, Pre-Baked Speculaas Struesel
3. Preheat your oven to 350° and place a rack in the middle of the oven.
4. Using a food processor (or a zip-lock bag and a rolling pin), crush the speculaas cookies until they are finely ground and have small crumbles, and then pour them into a large bowl.
5. Add 3/4 cup (90 grams) all-purpose flour, 1/3 cup (80 g) packed light brown sugar, ¼ tsp baking powder, and ¼ tsp kosher salt to the bowl, and mix until combined.
6. Add 6 tbsp (85 g) cold, unsalted butter, cubed to the dry ingredients. Toss until coated, and then using your hands, keep smashing the butter into the dry ingredients until the butter and the dry ingredients are combined and clumping together like moist sand.
7. On a parchment-lined baking sheet, crumble and spread out the streusel, leaving some chunks but not too big.
8. Place the baking sheet in the preheated oven on the middle rack and bake for 15 – 17 minutes.
9. Cool completely, break up any large chunks, and set aside to cool completely. (can be refrigerated for up to 3 days before using)
10. Blind Baked Crust:
11. Preheat oven to 350°F (180°C).
12. In a medium bowl, stir together 3 cups (312 grams) finely ground speculaas cookies, and 2 tablespoons (24 grams) sugar. Add 1 stick/ ½ cup (113 grams) unsalted butter, melted, and stir until well combined. Pour the crumb/sugar/butter mixture into your 9-inch deep-dish pie plate, and using a measuring cup, press the mixture into the bottom and up sides.
13. Bake until lightly toasted and fragrant, 10 to 12 minutes.
14. Let cool completely on a wire rack.
15. Make the plum puree:
16. Wash the plums and remove any grocery stickers you may find but keep the skins on. With a sharp paring knife, cut the plums in half and remove the pits, then chop the plums into quarters, and put all plums into a large saucepan or stock pot with plenty of room for stirring. (I used a high-sided stock pot).
17. Add 1 cup (200 g) of granulated sugar and stir until the plums are coated with sugar. Set aside to macerate for 15 minutes (or overnight in the refrigerator).
18. Return the pot to the stove, and over medium-high heat, add 2 cinnamon sticks, and cook the plums and all the accumulated juices and sugar, stirring often. Keep cooking until the plums are soft and the juices have been released. (about 15 minutes)
19. Once the plums have broken down and are soft, remove them from the heat and remove the 2 cinnamon sticks.
20. Using a stick blender, whir the plums into a puree until it is a smooth consistency (I prefer to keep pureeing it until there are no lumps whatsoever, but you could keep some larger fruit bits if you like that).
21. Carefully measure 1 ½ cups of the puree into a small bowl or measuring beaker and set aside to cool completely. (Can be refrigerated for up to 3 days) Leave the rest of the plum puree in the pot.
22. In a small bowl, mix the last ½ cup (100 g) of granulated sugar, and ½ cup (28 g) cornstarch together, until well combined.
23. Return the pot to the stove, and over medium-high heat, return the plum puree to a strong simmer (almost boil, but protect yourself from splatters). Once the puree is almost boiling, add the sugar and cornstarch mixture, and whisk into the hot puree, stirring constantly until the puree is thickened to pudding consistency and the cornstarch is cooked out.
24. Fill the pre-baked crust with the plum filling, about 2/3 full. (Any leftover pie filling is delicious as a cookie dip with the Bischoff cookies!)
25. Set the pie aside to cool completely and refrigerate.
26. Plum Mousse:
27. In a small bowl, add 2 tbsp cold water, and sprinkle the gelatin in the water and mix. Set aside for 5 minutes and allow the gelatin to bloom.
28. Once the gelatin has bloomed and soaked up all the water, place the bowl into a microwave for 10 seconds to carefully melt the gelatin. (you can also do this in a small saucepan, on medium-low heat. DO NOT BOIL. Gelatin is fragile, and you don’t want to overheat it.)
29. When the gelatin is melted, pour this into the puree you set aside previously and mix until the gelatin is completely incorporated, then continue with #31 . This can not be done ahead, do not let this sit for too long.
30. (If using Agar Agar instead of regular powdered gelatin, in a small saucepan bring ¼ cup water to a boil. Add 1 tsp of Agar Agar powder to the boiling water and stir while you bring it back to a boil. Be sure it reaches a boil for 2 minutes. While it’s still hot, pour this into the puree you set aside previously, then continue with the rest of the instructions)
31. In the bowl of a stand mixer, add 2 cups (480 g) heavy whipping cream, ¼ cup powdered sugar, a splash of vanilla extract, and whisk until soft peaks form. (or, you can use a hand mixer to whip to soft peaks)
32. After you have the cream whipped, add 1/3 of the puree with the gelatin (or agar agar) in it, and fold into the cream as gently as possible.
33. Then, add the rest of the cold plum puree/gelatin mixture, and fold gently until there are no streaks of white. There will be small bits of plum skin in the mousse, but this is normal.
34. Assembly
35. Add a layer of the pre-baked speculaas streusel on top of the filling, covering it completely. It might look like the pie is full, but the mousse will fill in all the gaps and sit on top of the streusel crunch. (Any leftover can be used as a garnish on top, or along with the plum filling leftover cookie dip!)
36. Carefully scoop the mousse on top of the speculaas streusel in the pie pan. If you have a deep dish pie pan, you should be able to put all of the mousse into the pan on top of the streusel. Smooth the top.
37. Set the pie into the refrigerator to set completely, 4 hours or overnight.
38. Topping and Serving
39. When ready to serve, add the remaining 2 cups (480 g) of heavy cream, the remaining ¼ cup of powdered sugar, and a splash of vanilla extract in the bowl of a stand mixer with a whisk attachment (or use a hand mixer) to whip the cream to stiff peaks.
40. Garnish the cold set pie with dollops of whipped cream, or pipe cream rosettes or a cream rope on top of the pie. Add any streusel leftovers to the top if you want, or use Bischoff Cookies for a decorative finishing.
41. Serve pie cold, and enjoy!