Melt butter in a large saucepan or pot over medium-low heat
Add the onions and cook, stirring frequently, until they reduce by half and become translucent
Add the thyme, beef stock, and sherry. Season with salt and pepper. Simmer on low for 30 minutes
Pierce potatoes with a fork and coat them in olive oil
Bake potatoes at 425°F for an hour
Slice off the top and carefully scoop out the inside of each potato
Add scooped potato to a bowl with grated Gruyère cheese, parsley, sour cream or creme fraiche, garlic butter, onion powder, garlic powder and a pinch of salt
Transfer mixture to a piping bag or Ziploc bag
Ladle the soup and onions into the hollowed out potato
Add some of the mashed potato mixture on top
Place Swiss cheese pieces on top of the mashed potatoes
Bake in a 450 degree oven for about 10 minutes or until the top is golden brown and cheese is melted
