Preheat the oven to 325 degrees F (170 degrees C). Arrange tart shells on a baking sheet.
Beat sugar, butter, and eggs together in a large bowl with an electric mixer until creamy. Stir in raisins, walnuts, and cream until thoroughly combined. Spoon batter into tart shells, no more than half full.
Bake tarts in the preheated oven until pastry is golden and filling is set, 20 to 25 minutes. Allow tarts to cool on a wire rack.