Preheat the oven: Preheat your oven to 325°F (160°C). Grease a 9-inch springform pan or line the bottom with parchment paper.

Prepare the crust: In a medium bowl, combine the almond flour, melted butter, powdered erythritol, and vanilla extract. Mix until the mixture resembles wet sand. Press the mixture evenly into the bottom of the prepared springform pan to form the crust. Bake the crust in the preheated oven for 8-10 minutes, until it's lightly golden. Remove and let it cool.

Make the cheesecake filling: In a large mixing bowl, beat the softened cream cheese and powdered erythritol until smooth and creamy. Add the eggs, one at a time, beating well after each addition. Stir in the sour cream, heavy cream, Irish cream-flavored syrup (or Irish whiskey with liquid stevia), vanilla extract, and instant coffee granules (if using). Mix until everything is well combined and smooth.

Bake the cheesecake: Pour the filling over the cooled almond flour crust. Smooth the top with a spatula. Bake in the preheated oven for 45-55 minutes, or until the edges are set but the center is slightly jiggly. Turn off the oven, crack the oven door slightly, and let the cheesecake cool in the oven for about 1 hour. This helps prevent cracks.

Chill and serve: Once the cheesecake has cooled, refrigerate for at least 4 hours, preferably overnight, to set completely. Before serving, garnish with whipped cream or a drizzle of sugar-free chocolate syrup if desired.