In a microwave safe bowl, melt the peanut butter and butter together in short bursts, stirring until smooth.
In a medium bowl, whisk together the almond flour, sweetener, and baking powder.
Stir in the eggs, vanilla extract, peanut butter mixture, and water until well combined. Stir in the chocolate chips.
Divide among 6 ramekins or mugs and microwave each for about 1 minute, until puffed and set. Serve warm.
Notes
Storage Information: Cover extra mug cakes tightly and store at room temperature for 1 day. You can also store them in the refrigerator for up to 5 days. To reheat, place it in the microwave for 15-20 seconds until just warm.