Melt 1 tablespoon butter in a pot.Cook onion until softened, add garlic and cook about 30 seconds.
Stir in 2 cups cream, 1 cup broth, Yukon Gold potatoes, nutmeg, salt, and pepper. Bring to boil, then reduce heat to medium and simmer until potatoes are translucent at edges and mixture is slightly thickened turn off heat and add lemon juice
Transfer potato mixture to 4.25 quart cassorole dish and bake 20 minutes.
While that is baking, melt 2 tbls of butter in a skillet, cook shredded potatoes about 2 minutes.
In a bowl mix 1/2 cup of cream, 1/2 cup of broth, and the parsley stir and add to shredded potatoes in the skillet, cook, stirring occasionally, until liquid has evaporated, turn off the heat, stir in 1 cup cheese
Remove baking dish from oven and top with shredded potato mixture. Sprinkle with 1/4 cup of cheese and bake until top is golden brown, about 20 minutes. Let cool 15 minutes.