Preheat oven to 400 degrees and butter twelve 1/4 cup muffin tins.

In a large bowl whisk together flours, baking powder, salt and thyme. Stir in walnuts and cheddar until combined well. In a bowl whisk together remaining ingredients and add to flour mixture, stirring just until combined (do not overmix).

Divide batter among muffin tins and bake in middle of oven for 15 minutes or until golden and a tester comes out clean. Cool muffins in tins on a rack 10 minutes and turn out onto rack.