Passover Brownies

Preheat oven to 325 degrees. Butter an 8x8 inch baking pan. Combine chocolate and butter in a small saucepan. Melt over low heat, stirring until smooth. Remove pan from heat and cool 10 minutes. Whisk together cocoa and Passover meal in a small bowl. Beat eggs and sugar in a large bowl until light and fluffy. Beat in sour cream and melted chocolate mixture. Beat in cocoa mixture on low speed until just combined. Stir in chocolate chips and walnuts. Scrape batter into prepared pan and spread evenly. Bake about 35 minutes until a toothpick comes out almost clean. Transfer brownies to a rack and cool completely. Cut into squares.