Preheat oven to 375°F. Preheat 9” x 13” casserole dish in oven while prepping kugel.
Lay out bacon on a baking sheet and bake for 15 minutes or until crispy. Reserve bacon fat.
Whisk together eggs, cream, 1 Tbsp kosher salt, pepper and nutmeg. Set aside.
Fill a pot up with cold water and 1 Tbsp salt. Peel russet potatoes and put in pot so they don’t oxidize before shredding them.
Shred onions with hand grater or food processor with large shredder attachment. Squeeze all liquid out of the shredded onions and place onions in a large bowl. Repeat process for potatoes.
Once bacon is crispy and at room temperature, chop and toss with Gruyère cheese. Reserve ¾ c of bacon and cheese mixture and set aside.
Mix tapioca starch and remaining bacon and cheese mixture in the large bowl with the potatoes and onions.
Whisk egg mixture again before pouring over potato mixture. Mix until well combined.
Remove preheated casserole dish from oven and brush all sides with reserved bacon fat. Careful, remember that casserole dish just came out of the oven so it's HOT!
Carefully pour potato mixture into casserole or baking dish and spread out evenly.
Bake for 1 ½ hours. Sprinkle the reserved cheese/bacon mixture and bake for an additional 10 minutes for cheese to melt and begins to turn golden-brown. Let potato casserole rest for 5 minutes before cutting and serving. Enjoy!