Hot Caramelized Onion Dip with Bacon and Gruyère

INGREDIENTS

• 2 teaspoons butter
• 1 teaspoon vegetable oil
• 2 Spanish onions (about 1 pound), halved and thinly sliced
• 1/4 teaspoon sugar
• 1/4 teaspoon sea salt
• 1 tablespoon sherry vinegar
• 1/2 teaspoon minced fresh thyme
• 3 applewood-smoked bacon strips
• 3/4 cup (3 ounces) shredded Gruyère cheese
• 1/2 cup sour cream
• 1/2 cup mayonnaise
• 1/4 teaspoon freshly ground black pepper