Grease the insert of a 6 quart slow cooker well.
In a medium bowl, whisk together almond flour, sweetener, cocoa powder, whey protein powder, baking powder and salt.
Stir in butter, eggs, almond milk and vanilla extract until well combined, then stir in chocolate chips, if using.
Pour into prepared insert and cook on low for 2 to 2 1/2 hours. It will be gooey and like a pudding cake at 2 hours, and more cakey at 2 1/2 hours.
Turn slow cooker off and let cool 20 to 30 minutes, then cut into pieces and serve warm. Serve with lightly sweetened whipped cream.