How to Make It
Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, sugar, cocoa, and salt, stirring with a whisk.
Combine canola oil and next 3 ingredients (through eggs), stirring with a whisk. Add to dry ingredients, stirring until blended. Stir in melted chocolate. Stir in walnuts.
Coat a 3-quart electric slow cooker with cooking spray. Pour batter into slow cooker. Cover and cook on LOW for 2 to 2 1/2 hours or until set around edges but still soft in the center. Turn off slow cooker. Let stand, covered, 30 minutes before serving. Sprinkle with powdered sugar, if desired.
Cooking Light Slow Cooker Tonight