Lightly coat 6 jumbo (3-1/2-inch) muffin cups with cooking spray or line with paper bake cups. Set aside.
In a mixing bowl, combine the flour, baking powder, baking soda, and salt. Cut in the shortening until the mixture is crumbly.
In another bowl, stir together the sour cream or yogurt, the 1/2 cup sugar, the milk, and egg. Add to the dry ingredients and stir until just combined.
Stir together the brown sugar, nuts, the 2 tablespoons sugar, and cinnamon.
Spoon half the batter into prepared muffin cups. Sprinkle half of the nut mixture into cups. Top with remaining batter and the remaining nut mixture.
Bake in a 350 degree F oven for about 25 minutes or until a toothpick inserted in center comes out clean. Cool 15 minutes in pan on wire rack. Remove from pan and serve warm.
For standard-size muffins, use twelve regular (2-1/2-inch) muffin cups; divide batter evenly as above. Bake in 400 degree F oven for 15 to 18 minutes. Cool 5 minutes. Remove from pans and serve warm.