Preheat the oven to 350°F. Crush vanilla wafers into crumbs, then mix with 6 Tbsp. melted butter and 1 cup sugar. Press into a parchment-lined springform pan and bake for 12 minutes. Freeze to chill.

For the cheesecake, mix cream cheese with 1 cup sugar until smooth. Add 2 eggs, sour cream, 2 Tbsp. vanilla extract, 1 Tbsp. lemon extract and a pinch of salt. Set aside.

Boil 4 sweet potatoes until fork-tender (15-20 minutes). Cool, peel, and mash. Mix in brown sugar, 1 cup sugar, 1 Tbsp. vanilla extract, 1 Tbsp. lemon extract, 4 Tbsp. melted butter, 2 eggs and milk.

Remove crust from the freezer. Layer half the cheesecake mixture, the sweet potato mixture then the remaining cheesecake mixture. Top with sweet potato dollops and swirl with a toothpick.

Place a water-filled pan on the bottom oven rack and bake the cheesecake for 90 minutes. Let cool for 10 minutes, then refrigerate for 8 hours or overnight. Top with whipped cream before serving.

When storing the cheesecake, wrap tightly in plastic wrap to prevent it from drying out and absorbing other odors in the fridge. Store in the refrigerator for up to 5-7 days. For freezing portions, slice the cheesecake and wrap each piece individually in plastic wrap. After wrapping in plastic wrap, cover with aluminum foil or place the wrapped cheesecake (or slices) in a freezer-safe airtight container.

Cheesecake can be frozen for up to 2-3 months. When ready to eat, thaw the cheesecake in the refrigerator overnight. Avoid thawing at room temperature to prevent texture changes.