*Makes 2-3 dozen cookies
2 cups all-purpose flour
2/3 cup cocoa powder
1 teaspoon baking powder
1/2 teaspoon baking soda
1/8 teaspoon salt
3/4 cup (1 1/2 sticks) butter, softened
1 1/3 cups granulated sugar
2 large eggs
1 1/2 teaspoons vanilla extract
2/3 cup sour cream
1 cup semisweet chocolate chips
4 ounces white chocolate, chopped
Preheat the oven to 350 degrees. Lightly grease two baking sheets (or line them with parchment or silpat liners).
Sift together the flour, cocoa powder, baking powder, baking soda and salt into a medium bowl. Gently whisk together to blend.
In the bowl of an electric mixer, beat the butter and sugar together at medium speed until light, about 2 minutes. Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as necessary. Mix in the vanilla extract. At low speed, add 1/3 of the dry ingredients and mix. Then add 1/2 of the sour cream and mix. Add another 1/3 of the dry ingredients followed by the remainder of the sour cream. Finally add the last of the dry ingredients and mix until just combined. Using a wooden spoon stir in the chocolate chips.
Drop the dough by tablespoonfuls onto the prepared baking sheets, spacing the cookies 1 inch apart. Bake the cookies for 12-13 minutes until edges appear done and no impression is left when you touch a cookie very lightly with a finger. Do not overbake or the cookies will be dry! Transfer the cookies to a wire rack and cool completely.
In a microwave-safe bowl, melt the white chocolate for one minute at 50% power. Stir and melt in 20-second intervals at 50% power, stirring after every interval, until chocolate is melted and smooth. (Don't cook at too high of a power or the chocolate will scorch and seize.)
Scrape the melted chocolate into a ziploc bag and seal the bag. Cut a tiny hole in one of the bottom corners of the bag and drizzle the cookies with the white chocolate in thin parallel lines. Refrigerate the cookies for 5 minutes or until set.
The cookies can be stored in an airtight container at room temperature for up to five days, although, in my opinion, these taste best within the first 1-2 days.