Blueberries N Walnut Brownie Cookies

Ingredients -

Butter - 1/2 cup softened
Powdered sugar - 2 cups
Unsweetened cooking chocolate - 1 cup coarsely chopped
Eggs - 4 at room temperature
Vanilla essence - 2 tsp 
Walnut pieces - 1/2  cup
Blue berries - 1/4 cup
All purpose flour - 2 cups
Baking powder - 2 tsp
Salt - 1/2 tsp
Powdered sugar, for coating

Method -

1. Melt chocolate and butter on a double boiler until its
    melted completely, remove it from the boiler, let it
    cool partially and beat it with a wooden spatula until
    smooth.
2. In another bowl beat sugar and eggs on a high speed
    with an electric mixer for 4-5 minutes until it's light and
    double in volume.
3. Blend the slightly cooled chocolate and vanilla essence
    into it, add  the walnut and blueberries too.
4. Sift the flour, baking powder and salt and mix into 
    the chocolate mix with a wooden spatula, half at a time
    until the dough is all mixed and smooth.
5. Cover it with foil or a cling film and refrigerate it or
    3-4 hours.
6. Heat the oven to 300 degrees. Grease the drip tray 
    and line them with parchment paper. 
7. Put about 1 cup of powdered sugar in a small bowl. 
    Now shape the dough into 1-1/2-inch-thick balls,
    applying little oil on your palms. Generously coat 
    each one with sugar and place it on a baking sheet,
    baking about 4-5 cookies at a time. 
8. Bake for about 10 minutes or until brown on both
    the sides, when done, the cookies will be puffed and 
    will feel very soft to the touch. Do not overbake.
8. Transfer it to a wire rack and let it cool, store it in
    an air tight container.