Chocolate Hazelnut Sandwich Cookies

Happy Mother's Day! Here is what I made for my wonderful mother and brother.

The recipe is a variation on one from 101cookbooks. She put only the melted chocolate in the middle of the cookies, but when I made a batch like that they tasted a little dry and a little too plain. I knew that they had more potential, and thought nutella and chopped hazelnuts would be a big improvement. I'm thinking of doing a caramel sandwich cookie next time, maybe even with chopped up heath bar in the middle too.

2 1/2 cups whole wheat pastry flour
1 teaspoon baking powder
scant 1 teaspoon salt
2 tablespoons + 1 teaspoon poppy seeds
6 ounces (1 1/2 sticks) unsalted butter, room temperature
2/3 cup brown sugar
2 large egg yolks
1 tablespoon vanilla extract
2-3 tablespoons milk

chocolate chips
nutella
hazelnuts

Preheat oven to 350º.
In medium bowl whisk together the flour, baking powder, salt and poppy seeds. Set aside.
In a separate bowl, beat butter until fluffy and creamy. Add sugar and mix some more, scraping sides of bowl along the way.
Mix in egg yolks and vanilla extract, scraping sides again if needed.
Being careful not to over-mix, stir in flour mixture by hand. If the dough is on the dry side stir in the milk as well.
Turn the dough out onto the counter-top, knead it once or twice (just so it comes together) and form one large ball.
Cut the dough into four quarters, then shape each piece into a ball. Flatten each of the four balls into 1/2-inch thick pancakes, and wrap each piece individually in plastic.
Chill in the refrigerator for at least a half an hour.

Roll out the dough thin as can be on a lightly floured surface (or on parchment paper) - wafer thin, about 1/8 inch, and stamp out using a cookie cutter.
Arrange cookies 1 inch apart on prepared baking sheets.
Bake for about seven minutes on a parchment-lined baking sheet or until the cookie edges are golden brown.
Remove from oven and cool completely on a rack.

Melt the chocolate (in a double boiler or a bowl placed over a bit of simmering water).
Toast and finely chop hazelnuts.
Mix nutella, hazelnuts, and chocolate.
Spread mixture onto the flat side of one cookie. Top with another cookie - matching flat side to flat side. Repeat with the remaining cookies, setting them aside to let the chocolate set.