In the basin of a 4- to 5-quart slow cooker, combine the potato pieces, undrained vegetarian baked beans, frozen corn, vegetable broth, chili powder, and unsweetened cocoa powder.
Stir everything together to ensure the spices are evenly distributed.
Secure the lid and cook on the LOW setting for 8 to 9 hours or on the HIGH setting for 4 to 4. 5 hours, until the potatoes are perfectly tender.
Ladle the hot stew into bowls.
Top each serving generously with shredded cheddar cheese and a dollop of sour cream before serving.