Instructions: Preheat the oven to 325 degrees. Lightly grease a 12-by18 inch baking pan and line with parchment paper.

Melt the butter and chocolate in the top of a double boiler over hot water.

Keep warm and set aside.

Sift together the flour, baking powder and salt. Set aside.

In a large mixing bowl, combine the sugar, eggs, sour cream and vanilla. Stir until well-combined. Stir in the melted butter and chocolate mixture.

Add the flour mixture and stir until well-combined. Fold in the chocolate chips and nuts if desired.

Bake for 35 to 45 minutes. Center will be slightly soft. Cool and cut into bars.

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