Preheat oven to 400 degrees F (200 degrees C). Pierce potatoes with a fork and bake until soft, about 1 hour. Remove from oven and cool until potatoes can be handled, about 20 minutes.
Reduce oven temperature to 350 degrees F (175 degrees C). Grease a large baking sheet.
Meanwhile, place olive oil in small skillet over medium heat. Add shallots and cook and stir until softened and beginning to brown, about 10 minutes. Set aside.
Cut potatoes in half lengthwise and scoop out pulp, leaving a thin shell. Set shells aside. Place pulp into a blender or food processor and blend until smooth. Add ricotta, salt, pepper, ginger, and sugar to the blender; blend until smooth.
Return potato mixture to a bowl; stir in shallots, Parmesan cheese, and sage. Spoon mixture back into potato skins. Place potatoes on prepared baking sheet.