Sweet potato cheese squares

Ingredients:
700 g sweet potatoes            
250 g Graham crackers            
1 cup sugar                
130 g unsalted butter (melted)        
¼ tsp salt                     
1½ cups ricotta cheese            
½ cup low-fat yoghurt
4 eggs                 
Lightly sweetened whipped cream, for serving
Method:
Preheat oven to 375⁰ F. Bake sweet potatoes for about 1 hour, until tender. Remove from oven, allow to cool slightly then discard skins and mash the flesh with a fork. In a blender, whisk the crackers until finely ground. Add ⅓ cup sugar, 115 g butter, and a pinch of salt, and blend again until combined well. Firmly press the mixture into a 9”*13" baking dish. Bake until the crust is dry and set, for about 12 minutes. Remove from oven and reduce temperature to 325⁰ F.
In a clean food processor, puree the sweet potatoes, ricotta, yoghurt, eggs, ¼ tsp salt, and add in the remaining butter and sugar. Pour over the crust, and bake until just set in center, for 30 to 35 minutes. Let cool on a wire rack, then refrigerate until cold. Cut into squares and top with whipped cream.