Place the unpeeled garlic cloves directly into the crockpot, spreading them evenly at the bottom. Drizzle with a teaspoon of olive oil and set the cooker to low. Let the garlic roast for about 6 hours until soft, fragrant, and golden.
Meanwhile, peel and chop the potatoes into roughly one-inch pieces, and dice the onion to prepare for cooking.
Once the garlic has roasted, carefully remove the cloves from their skins, pressing gently to release the softened, sweetened garlic into a small bowl.
Add the chopped potatoes, diced onion, roasted garlic, vegetable broth, and olive oil to the crockpot. Stir everything together to combine nicely.
Set the crockpot to low and cook for 5-6 hours, until the potatoes are fork-tender and the flavors meld beautifully.
Use an immersion blender directly in the crockpot or carefully transfer the chunky soup to a blender. Puree the soup until silky smooth, then return it to the crockpot if needed.
Stir in the milk or cream to add richness, season with salt and pepper to taste, and adjust the thickness with more broth if desired.
Let the soup simmer uncovered for another 10-15 minutes to meld the flavors and warm through. The final consistency should be velvety and inviting.
Spoon the hot, creamy soup into bowls, garnish with fresh herbs if you like, and enjoy this comforting, velvety meal.
