Boil the apple cider with mulling spices in a large pot on high heat for about 1 hour until reduced to a thick syrup, yielding about 1/3 cup. Set aside to cool.

Preheat the oven to 350°F (180°C).

Crush the digestive cookies or graham crackers in a food processor and mix with melted butter, salt, and powdered sugar until resembling wet sand.

Press the crumb mixture into an 8-inch round springform pan lined with parchment paper and bake for 10 minutes. Cool and refrigerate.

Lower the oven temperature to 325°F (163°C).

In a stand mixer, beat the softened cream cheese and brown sugar until smooth.

Add sour cream, vanilla extract, salt, cinnamon, and cooled reduced apple cider, mixing until creamy.

Add eggs one at a time, mixing just until combined, then fold in the flour.

Place the cheesecake pan inside a larger 13×9 inch pan filled with hot water halfway up the sides.

Pour the filling into the crust and bake for 90 minutes, or until the edges are set but the middle wobbles slightly.

Turn off the oven, crack the door open with a wooden spoon, and let the cheesecake cool for 30 minutes before removing from the oven.

After cooling, let it sit at room temperature, then refrigerate for at least 8 hours or overnight before serving.