Mix together the cream cheese and gruyere in the bowl of a food processor and process all of it until it becomes smooth.

Heat oil in a large skillet on medium heat. Add the onion, the sugar, the salt, and the pepper to the pan and stir frequently until the liquid is released and the onions are opaque. Stir in the sherry vinegar to deglaze the pan, then take it off the heat and let it cool to room temperature.

Stir the onion mixture and the onion soup mix together with the cheese mixture and mix until evenly incorporated, then scrape the cream cheese mixture onto a parchment paper-lined baking sheet.

Lightly moisten your hands with water, then shape the cream cheese mixture into a ball, and wrap in plastic wrap. Leave it in the fridge for 45 minutes to an hour, or until it can be easily rolled.

Coarsely chop about 1/2 of the baguette into pieces and reserve the remaining half for serving. Place the chopped baguette in the food processor bowl and pulse until fine crumbs form. Heat a cast-iron pan over medium-high heat and add the butter to the pan. Once it's melted, stir in the baguette crumbs and cook, stirring frequently, until they turn golden brown. Toss the bread crumbs with thyme.

Spread the bread crumb mixture evenly on a rimmed baking sheet and roll the cheese ball in the crumb mixture to evenly coat.

Place cheese ball on a serving platter and serve with additional sliced baguette for dipping and scooping.