To make the crust mix the cookie crumbs, melted butter and erythritol together and press mixture firmly into the bottom and sides of tart pan.
Pulse the walnuts and chocolate chips in a food processor until they are the texture of coarse crumbs. Set aside 2 tablespoons of chocolate walnut mixture to decorate the tart.
Sprinkle the rest of the chocolate walnut mixture over the crust and lightly press it in.
Chill the crust in the freezer while you make the filling
In a large mixing bowl combine 1/2 cup of the heavy cream with the almond milk, erythritol and Keto Chow and beat until all the Keto Chow is dissolved and the mixture is light and fluffy.
Add the remaining cup of heavy cream and beat until doubled in volume and stiff peaks form.
Spread the filling into the prepared crust and sprinkle with the reserved chocolate walnut mixture.
Chill at least 30 minutes before serving.
To serve, lift the bottom out of the tart pan, transfer the tart to a serving tray and cut into pieces.
Store the tart tightly wrapped in the refrigerator for up to three days.