Line the bottom of a 9-inch springform pan with ladyfingers. Trim the bottoms of 20 ladyfingers and arrange vertically around the inside of the pan, with the cut end down so ladyfingers stand. Use cut pieces to fill in gaps in bottom crust. (You may need to cut more for the edges, or have extra cookies left over.)

In a large bowl, beat together ricotta cheese and granulated sugar until combined. Set aside.

In the bowl of a stand mixer, beat 1 3/4 cups whipping cream and powdered sugar until soft peaks form. Set aside 1/2 cup of whipped cream and fold remaining whipped cream into the cheese mixture.

In another bowl, beat together pudding mix, cinnamon, ginger, cardamom, grated nutmeg, pumpkin, and milk. Fold in reserved ½ cup whipped cream.

Spread cheese mixture into the prepared pan, smoothing the top. Spread pumpkin mixture over the cheese mixture, doing so carefully as to preserve the layers. Cover and freeze for 4 hours or refrigerate overnight.

To serve, beat remaining 1/4 cup whipping cream to soft peaks, and dollop into the center of the charlotte. Sprinkle with grated nutmeg.