-chopped (*) (*) Place the walnuts in a single layer on a baking sheet and bake at 200ºC or about 5 minutes, shaking the sheet a couple of times. Preheat oven to 400 degrees. Lightly butter twelve 3-by- 3 cm muffin cups. In a medium saucepan, over low heat, melt the butter and unsweetened chocolate. Remove the pan from the heat and cool the mixture until tepid. In a large bowl, stir together the flour, baking soda and salt. In another bowl, stir together the buttermilk and brown sugar until smooth. Then stir in the chocolate/butter mixture, egg and vanilla until combined. Make a well in the center of the flour mixture. Add the liquid ingredients and stir just to combine. Stir in the chocolates and walnuts. Spoon the batter evenly among the prepared muffin cups. Bake 19 to 22 minutes, or until a cake tester or toothpick inserted into the center of one muffin comes out with a few crumbs remaining. Remove the muffin tin or tins to a wire rack. Cool the muffins in the pan(s) for 5 minutes. Remove the muffins from the cups and finish cooling on the rack. Serve warm or cool completely. Store the muffins in an airtight container at room temperature. Makes about dozen muffins.