Ingredients
5 pounds onions, very thinly sliced
12 thyme sprigs, picked and minced
6 ounces butter
Olive oil
Salt and pepper
1 cup buttermilk, plus more if needed
2 cups sour cream
1 cup Duke’s mayonnaise
¼-½ cup sherry vinegar
Directions
- Preheat oven to 400 degrees. Add onions, butter, olive oil, and thyme to a nonstick dutch oven and cover with lid. Bake for 45 minutes, stirring every 15, until onions are deeply caramelized. Remove from oven and cool to room temperature.
- In a blender or food processor, purée onions with buttermilk. Add sour cream, mayonnaise, and sherry vinegar and puree until very smooth, adding more buttermilk if necessary.
- Adjust acidity with more vinegar, and season with salt and pepper.
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