Prepare the Slow Cooker & Pan: Preheat a 5- to 6-quart slow cooker.
Pour in 1 cup / 240 ml of boiling water and place a spacer inside (like a small rack or crumpled foil).
Line the bottom of a medium springform pan with parchment paper, ensuring it fits in the cooker without touching the water.
Make the Crust: In a bowl, combine all crust : almond flour, butter, erythritol, egg yolk, vanilla, and salt. Use your hands to mix until a dough forms, then press it evenly into the bottom of the prepared springform pan.
Mix the Cheesecake Filling: In a separate bowl, use a whisk or an electric mixer to beat the room-temperature cream cheese until smooth.
Add the sour cream, egg yolk, whole egg, erythritol, vanilla, lemon juice, lemon zest, and coconut flour.
Mix until just combined and smooth—do not overmix.
Add optional stevia if desired.
Pour the filling over the almond crust.
Cook the Cheesecake: Carefully place the springform pan onto the spacer in the slow cooker.
Cover and cook on low for 4 hours.
Cool Completely: Once cooked, turn off the slow cooker.
Remove the lid and let the cheesecake cool inside the slow cooker for 2 to 3 hours. This gradual cooling prevents cracks.
Chill Overnight: Transfer the cheesecake (still in its pan) to the refrigerator to chill and set completely, preferably overnight.
Prepare the Ganache: When ready to serve, gently run a blunt knife around the edge of the cheesecake and release it from the springform pan. To make the ganache, break the chocolate into small pieces and place in a heatproof bowl with the vanilla.
Heat the cream and butter in a small saucepan over medium heat until hot but not boiling.
Pour the hot cream mixture over the chocolate.
Let it sit for a minute, then stir until smooth and creamy.
Garnish and Serve: Let the ganache cool slightly, then pour it over the chilled cheesecake. Return the cheesecake to the fridge for at least 10 minutes to allow the ganache to set before slicing.
Mix the cheesecake filling until the are just combined. Overmixing incorporates too much air, which can cause the cheesecake to rise and then crack as it cools.