Heat the oven. Preheat to 325°F (163°C). Line a 24-cup mini muffin pan with paper liners.
Mix the crust. In a bowl, combine almond flour, sweetener, cinnamon, and salt.
Stir in melted butter and vanilla until the mixture resembles damp sand.
Press and par-bake. Divide crust among liners (about 1 tablespoon each). Press firmly with the back of a spoon. Bake 7–8 minutes until fragrant and just set.
Cool 5 minutes.
Make the filling. Beat cream cheese and sweetener until smooth and fluffy, 1–2 minutes. Add eggs one at a time, mixing just to combine. Blend in sour cream, vanilla, and salt until smooth.
Avoid overmixing.
Fill and bake. Spoon filling over crusts, almost to the top. Tap the pan to release air bubbles. Bake 12–15 minutes until edges are set and centers still jiggle slightly.
Cool slowly. Turn off the oven, crack the door, and let sit 10 minutes.
Transfer pan to a rack and cool to room temp. Refrigerate at least 2 hours to firm.
Make the chocolate topping. Gently melt chocolate chips with heavy cream over low heat or in short microwave bursts. Stir until glossy.
Add marshmallow layer. Spread or pipe a thin layer of sugar-free marshmallow creme over chilled cheesecakes.
If using mini sugar-free marshmallows, place a few on each bite.
Finish with chocolate. Spoon or drizzle warm ganache over the marshmallow layer. Add a pinch of flaky salt if you like. Chill 20 minutes to set.
Serve. Peel off the liners and enjoy cold or slightly chilled for the best texture.