Preheat the oven to 350°F (175°C).

Crush the Ritz crackers into fine crumbs and mix with softened butter and granulated sugar until well combined. Press into the bottom of a greased baking dish.

Roast the sweet potatoes in their skins until tender, about 45 minutes. Let them cool slightly.

Mash the roasted sweet potatoes until smooth.

Blend in the sugar, eggs, egg yolks, heavy cream, cinnamon, nutmeg, and vanilla until well combined.

Beat the egg whites with cream of tartar until stiff peaks form. Gently fold into the sweet potato mixture.

Pour the sweet potato filling over the crust, spreading it evenly.

Bake for 30-35 minutes, until filling is set and edges are slightly golden.

Cool in the baking dish before slicing into squares.

Optional: Dust with powdered sugar or top with whipped cream before serving.