Cover the potatoes in a large pot with just enough water to cover all of the potatoes, add salt, and bring to a boil. Boil your Yukon Gold potatoes until tender when forked (about 15 minutes), then remove from heat and drain the water.
Preheat your oven to 450 degrees F. Coat your baking sheet with olive oil (about 2 Tbsps) or line with parchment paper, then place your potatoes on the baking sheet. Using a masher, press down on each potato to flatten them out, but without breaking the potatoes apart. I usually mash once, then turn the masher 90 degrees to mash in an opposite direction.
Once flattened, season the potatoes with salt, pepper, and turmeric then top your Yukon Gold potatoes with the grated Gruyere Swiss cheese and crumbled bacon. Bake at 450 degrees F for 30-45 minutes (depending on the size of your potatoes). Once you can see golden crispy edges, your potatoes are ready to serve. Garnish with optional sour cream and green onions, if desired.