Preheat oven to 350 °F.
Arrange the thick-cut bacon on a walled cooking sheet lined with aluminum foil and cook until the bacon is crispy in about 25-30 minutes; make sure to rotate the bacon halfway through the cooking time to cook evenly. Remove the bacon when crispy and transfer the stripes to a plate or platter lined with paper towels to absorb excess drippings. Set the thick-cut bacon aside.
Adjust the oven to 375 °F.
Wash and rinse peel potatoes and shred the potatoes using a box grater. Wrap the shredded potatoes in a paper towel and/or a large cheesecloth or kitchen towel, and squeeze out as much water as you can.
Shred the onion using a box grater and use the same method to remove as much moisture as you can. I transfer onions into a fine-mesh sieve and, using the back of a tablespoon, pressed out as much water as I could. Set aside.
Mince garlic and parsley and set aside.
Grate one cup of smoked gouda and one cup of Gruyere cheese.
Transfer the shredded potatoes, onions, and minced garlic to a large mixing bowl and add heavy cream, melted butter, and cheeses.
Add sea salt and freshly cracked black peppercorns and mix thoroughly.
Place parchment lotus cups into a muffin pan, and fill each cup with the au gratin mixture.
Place the muffin pan on the middle rack of the preheated oven and bake at 375 for 30-40 minutes with 5 minutes remaining top each cup with more cheese and continue to bake until the potatoes are golden brown.
Remove from the oven and top each cup with thick-cut bacon; just before serving, top each cup with green onion and serve.