How to Make It
Heat a slow cooker on high until hot. Stir in the oil, onions, garlic, 3/4 teaspoon salt and 1/2 teaspoon pepper and cook, stirring occasionally until golden, about 6 minutes. Stir in the carrots, celery, stock, and split peas. Reduce the heat to low and cook until the split peas have fallen apart, 6 to 8 hours. Season the soup with salt and pepper to taste, then serve.