Preheat oven to 350 degrees. Grease two 9 x 5 loaf pans. Toast walnuts on a baking sheet for 3 to 5 minutes or until fragrant. Cool.

Melt chocolate by microwaving on medium for 25-second intervals, stirring in between, until smooth. Cool.

Cream butter and sugar. Beat in eggs one at a time. Mix in cooled chocolate. In a separate bowl, mix flour, baking soda and salt. Stir buttermilk and vanilla together. Add flour and buttermilk alternately to chocolate mixture. Stir in walnuts.

Divide batter between the two prepared pans. Bake for 55 to 60 minutes, or until knife or toothpick inserted in the center comes out clean. Cool bread in pans for 10 minutes, then remove from pans and cool on a wire rack. Serve warm or toasted with butter, it's like eating a warm brownie!