Slow-Cooker Caramelized Onions & Fennel

Combine the onions, fennel, oil, salt, 1 tablespoon of the thyme, and 2 teaspoons of the oregano in a 5- to 6-quart slow cooker, tossing to coat. Cover and cook on LOW until the vegetables are golden brown, about 12 hours. Uncover and stir gently. Increase the heat to HIGH, and cook, uncovered, until the mixture thickens, about 2 hours, stirring every 15 minutes. Stir in the vinegar, and the remaining 1 teaspoon thyme and 1/2 teaspoon oregano.