Melt the butter in a large pot over medium heat, and mix in the olive oil. Saute the onion, carrot, and red pepper for about 5 minutes, until onion is lightly browned. Stir in the garlic, and continue to cook 1 minute. Add in the broth, and bring to a boil. Place the potatoes in the pot, reduce heat to low, and cook 15 minutes, until potatoes are tender.
Add spices, salt, and pepper. Continue cooking until heated through.
Using an immersion blender, puree until smooth. Stir in the milk until mixed and creamy.
Notes
Vegan version: Substitute all olive oil for the butter and add a full quart (4 cups) of vegetable broth instead of half milk and half broth.