Preheat oven to 325F and butter a 9-inch springform pan. (if your springform pan is prone to leaking oil, place it on a cookie sheet)

In a microwave-safe bowl or glass measuring cup, melt butter and chocolate together in the microwave in 30-second increments. Whisk until smooth. Alternatively, you can melt them together over low heat in a small saucepan.

In a small bowl, whisk together almond flour, cocoa powder, and salt.

In a large bowl, beat eggs, sweetener, and vanilla until smooth. Beat in almond flour mixture, then butter/chocolate mixture until smooth. Stir in nuts.

Spread evenly over bottom of prepared pan. Bake 12 to 18 minutes until set around edges but still soft in the center. Let cool 15 to 20 minutes.

Reduce oven temperature to 300F.

In a large bowl, beat cream cheese until smooth. Beat in eggs, sweetener, cream and vanilla until well combined.

Pour filling over crust and place cheesecake on a large cookie sheet. Bake until edges are set and center just barely jiggles 35 to 45 minutes. Remove from oven and let cool.

Run a knife around edges to loosen and then remove sides of the pan. Cover with plastic wrap and refrigerate at least 3 hours.