In al arge skillet, heat 1 tbsp oil over medium-high heat. Add 1 bag of onions, the bay leaf and 1 thyme sprig. Cook, stirring occasionally, until onions begin to turn deep golden brown in spots, 6 to 8 min. Transfer to a bowl with a slotted spoon. Repeat with remaining 1 tbsp oil, onions and thyme sprig. Return first batch to skillet.
In a small bowl, stir together vinegar, wine, sugar and salt. Add to onions and bring to a boil. Reduce heat to medium-low and simmer, stirring occasionally, until liquid is the consistency of a syrup and onions are glazed, 20 to 25 min. discard bay leaf and stir in pepper. Garnish with thyme.
Use pearl onions from the frozen foods section at the grocer. So much easier that fresh!