Heat oil in a Dutch oven over medium heat. Add onion, carrot, celery, and garlic; cook and stir until onion is translucent, 5 to 7 minutes. Stir in broth, split peas, and seasoning blend; cover and bring to a boil. Reduce heat to low and simmer, stirring frequently, until split peas are tender, about 2 ½ hours.
Puree the soup with an immersion blender and serve.
