Toss potatoes, onion, garlic, bell pepper, and Cajun seasoning into your slow cooker.
Pour in the vegetable broth. Give it a quick stir to mix everything together.
Cover and cook on high for 3–4 hours or low for 6–7 hours, until the potatoes are fork-tender.
Use an immersion blender to blend part of the soup right in the pot, or transfer half to a blender and pulse, then return it to the cooker.
Stir in the coconut milk or cream. Let it warm through for another 15–20 minutes.
Taste and adjust seasoning with salt, pepper, or more Cajun spice.
Serve warm, topped with scallions if you’re feeling fancy.