Nutella Cookies...FAIL

Baking is science, so starting to make cookies from scratch at 12:30am can be disastrous if sleepy.
I got this recipe from Visions of Sugar Plums. Her recipe has simple ingredients and seemed easy to whip up, plus everyone lovese Nutella. I don't know what I was thinking and somehow thought '1/2 cup of butter = 2 sticks'. That's not right! 1/2 cup is 1 stick. Oh boy. When I was whipping the batter and spooning it onto the baking sheet, I was like "why does it feel like chocolate mousse?" I still had no idea what I did until the cookies came out of the oven. They still tasted fine, but they were really thin and ugly =/

Here's the recipe if you guys want to try to make it the correct way. Her cookies look so good on her blog:

Nutella Hazelnut Cookies

1/2 cup unsalted butter
2 ounces unsweetened chocolate, coarsely chopped
1 1/3 cups granulated sugar
1 3/4 cups all-purpose flour
1 teaspoon baking soda
3/4 teaspoon salt
3/4 cup Nutella
2 large eggs
2 teaspoons vanilla extract
1 cup coarsely chopped hazelnuts, toasted
Preheat oven to 350 degrees F. Grease cookie sheets.

Melt butter in a small saucepan over medium heat; cook butter, whisking frequently, until it turns golden brown and foams, about 3-4 minutes. Remove from heat and whisk in chocolate until melted. Place sugar in a large mixing bowl; add butter-chocolate mixture, and beat using a mixer on medium speed, until well combined and grainy - about 2 minutes.

In a medium mixing bowl, sift together flour, baking soda and salt. Beat Nutella, eggs and vanilla into sugar mixture, until well combined, about 1-2 minutes. Reduce mixer speed to low and beat in flour mixture until just combined; stir in hazelnuts until combined.

Roll tablespoons of dough into balls, place on cookie sheets, and flatten slightly using palms of hands. Bake for 12-14 minutes, or until set and slightly crisp. Cool 2 minutes before transferring to wire racks to cool completely.

Makes 3 dozen cookies