Wash and peel the potatoes and place them in a large pot. Cover potatoes with cold water and add one tablespoon of salt. Bring to a boil over medium heat and cook for 15 to 20 minutes or until tender. Drain the water and place potatoes in a large bowl.
Mash the potatoes using a fork or potato masher.
Heat the milk in a small saucepan.
Add the butter and heated milk to the mashed potatoes and mix with a wooden spoon. Season with salt, one tsp black pepper, and nutmeg. Do not overmix the potatoes. Set potato mixture aside.
Chop the crab sticks into smaller pieces. In a medium size bowl, mix the crab with the sliced onion, heavy cream, lemon juice, lemon zest, and one teaspoon black pepper (and hot sauce if desired).
Preheat oven to 400 degrees F.
Spoon one layer of the mashed potatoes in a baking dish or pie plate, then layer the crab mixture on top and finish by adding another layer of the mashed potatoes mixture on top.
Bake for 15 to 20 minutes until lightly golden on top. Serve warm.