In a large nonstick skillet, combine all the ingredients: pearl onions, cider vinegar, cubed butter, whiskey (or apple cider), maple syrup, dried thyme, kosher salt, pepper, and water. Stir everything together until the onions are evenly coated.

Set your skillet over medium-high heat and bring the mixture to a gentle boil, which typically takes about 3-5 minutes.

Once boiling, reduce the heat to medium-low and cover the skillet. Allow the onions to simmer for 6-8 minutes until they become fork-tender.

Uncover the skillet and increase the heat to medium-high. Cook for an additional 10-12 minutes, stirring occasionally, until the liquid reduces into a glossy glaze.

Once the liquid is almost evaporated, remove the skillet from heat and let the onions cool briefly before serving warm.