For the chocolate crust:

1. Preheat the oven to 350° F.
2. Combine the melted butter, almond flour, sweetener and cocoa powder in a medium sized bowl and mix well.
3. Transfer the crust dough to a 9 x 9 pan lined with parchment paper or foil (this will make removing the bars much easier.)
4. Press the crust firmly into the bottom of the pan.
5. Bake the crust for 8 minutes.
6. Remove from the oven and set aside to cool.

For the cheesecake filling:

1. Combine the cream cheese, eggs, sweetener, espresso powder, and vanilla extract in a blender and blend until smooth.
2. Pour over the par baked crust and spread out evenly in the pan.
3. Bake the cheesecake bars at 350° F for 25 minutes, or until set.
4. Remove from the oven and cool.
5. Dust with optional cocoa powder if using.
6. Chill for at least 1 hour, preferably longer, before cutting into four rows of squares to serve.
7. Store in an airtight container in the refrigerator for up to 5 days, or freeze for up to 3 months.