In a Dutch oven or large saucepan, melt butter and cook carrots and onions over low heat, covered about 8 minutes.
Add potato, bay leaf and stock. Simmer, covered, 40 minutes, stirring occasionally.
Discard bay leaf. In a food processor or blender, puree soup (in batches if necessary).
Return to pan and season with salt and pepper.
Serve hot and garnish is you like.
I have substituted carrots w/cut up butternut squash (you can buy the squash cut up at grocery stores. You need two packs 18 oz each). You can add curry to taste.