225g of butter, softened (1 cup)

265g of white chocolate chips, tossed with 2 TBS flour and 1 tsp cinnamon (1 1/2 cups)

(Or the equivalent in cinnamon chips tossed with 2 TBS flour)

You will also need:

4 TBS sugar

4 tsp cinnamon

Preheat the oven to 180*C/350*F/ gas mark4.  Butter two 9 by 5 inch loaf tins and dust lightly with flour, shaking out any excess.  Set aside.

Sift the flour, baking powder, and 2 tsp cinnamon together in a bowl.  Set aside.

Cream the butter and suar together until light and fluffy.  Beat in the eggs, one at a time.  Beat in the vanilla and sour cream.   Add the flour mixture, stirring just to combine.  Coat the chips with flour and cinnamon (if using white chocolate chips) and stir them into the batter.  
 

Mix together the final amount of sugar and cinnamon.  Spoon half of the batter into the prepared loaf tins.  Sprinkle half of the cinnamon sugar over top.  Spread the remaining batter over top.  Sprinkle with the remaining cinnamon sugar.  Take a round bladed knife and swirl gently cutting down in and up in the batter without mixing in the cinnamon sugar too much.

Bake for 60 to 70 minutes, or until a toothpick inserted in the centre comes out clean.  Allow to cool in the pans for ten minutes before tipping out to cool completely.