Prick the skin of the sweet potatoes with the tip of a knife in two or three places. Place in the microwave. Cook for 5 minutes on high and then flip sweet potatoes over and cook another 5 minutes. Prick with a fork, if there's resistance, the potato isn't fully cooked. Continue cooking for 2 minute intervals until cooked completely through. When cooked and soft, pull potatoes out of the microwave and let cool.

Preheat oven 375º. In a food processor, pulse graham crackers until crumbly. Add 1/3 cup sugar, 1/2 cup butter, 1/4 tsp. salt and pulse until combined. Firmly press mixture into the bottom of 9x13 baking dish. Bake until crust is dry and set, about 12 minutes. Pull out of oven and reduce temperature to 325º.

Peel skin off sweet potatoes and place in clean food processor. Pulse sweet potatoes until mashed and then add ricotta, yogurt, eggs, 1/4 tsp. salt, remaining 3 Tbsp. butter and remaining 2/3 cup sugar.

Pour sweet potato mixture into crust and bake at 325º until just set in the middle, 30 to 35 minutes. Let cool on a wire rack for 30 minutes, then refrigerate until cold, 1 hour or overnight. Cut into squares and serve with whipped cream!