Line the bottom of a 26 cm springform pan with parchment paper and grease the sides.
Drain the sour cherries over a bowl using a sieve, catching all that delicious cherry juice.
Preheat your oven to 175°C (conventional top/bottom heat).
Instructions:
Add all the shortcrust pastry ingredients to the mixing bowl and mix for 10 sec / Speed 5. Be careful not to overmix, or the dough will become too soft! It should look nicely crumbly.
Transfer the dough to your springform pan, press it evenly into the bottom with your hands, and work it about 3 cm up the sides to create a border.
Prick the crust several times with a fork, then pop it in the fridge to chill.
Next up, make the streusel! No need to rinse out the mixing bowl for this step.
Add all the streusel ingredients to the mixing bowl and blend for 10 sec / Speed 5 until buttery crumbs form.
Transfer the streusel to a bowl and set aside.
Clean the mixing bowl, then add 300 g of the reserved cherry juice along with the vanilla pudding powder and sugar. Cook for 6 min / 100°C / Speed 3.
Fold in the drained cherries and cook for another 2 min / 80°C / Reverse direction / Soft stir setting.
Pour the warm cherry filling into the chilled shortcrust base.
Scatter the streusel evenly over the top and bake on the lower rack of your oven for 50 minutes. If the streusel starts getting too brown toward the end, loosely tent the top with aluminum foil for the last 10 minutes.
Remove from the oven and let the cherry cake cool completely.
Insert the butterfly attachment! Add the cold heavy cream and whipped cream stabilizer to the mixing bowl and whip on Speed 3 until stiff peaks form. (It took me about 2 min 35 sec to reach perfect stiffness, but this depends on how cold your cream and bowl are. Keep a close eye on it starting at the 2-minute mark so you don't accidentally turn it into butter!).
Either spread the whipped cream directly over the top of the cooled cake, or transfer it to a piping bag fitted with a round tip and pipe pretty dollops all over.
Finish with a light dusting of unsweetened cocoa powder right before serving. Enjoy!
Notes
To keep the streusel topping perfectly crisp, it's best to spread the whipped cream over the cake right before serving.