Heat olive oil in a large pot over medium heat. Add the onion, carrots, and celery. Cook for 6 to 8 minutes, stirring often, until softened and lightly golden.
Stir in the garlic, bay leaf, dried thyme, salt, and black pepper. Cook for 30 seconds until fragrant.
Add the rinsed split peas and vegetable broth. Stir well to combine.
Bring the soup to a gentle boil, then reduce heat to low. Simmer uncovered for 40 to 45 minutes, stirring occasionally, until the split peas are soft and the soup thickens.
Remove the bay leaf. For a thicker or creamier soup, blend a portion using an immersion blender. Add water as needed to reach your preferred consistency.
Adjust seasoning if needed. Serve hot.
