A classic from my Grandma's recipe box, you can't go wrong with these shortbread chocolate delights. I had at least 5 (probably 8) immediately after they cooled... they're dangerously good (honestly like crack). Perfect for a party or bringing into work (if you like your coworkers that much)!
Preheat oven to 350 degrees and grease a small cookie sheet (11x10 or equivalent).
In large bowl, mix butter and brown sugar until creamy consistency.
Add in egg yolk and vanilla. Mix well.
Sift in flour and baking powder. Mix until just combined.
Spread dough into greased cookie sheet. Bake in oven for 25-30 minutes. Cookie layer is done when slightly golden brown around the edges.
Immediately after taking cookie sheet out of the oven, sprinkle the chocolate bits across the surface. (I use chocolate chips but you can use a chopped up chocolate bar).
Let the chocolate sit for a minute, then spread the chocolate evenly across the cookie. BONUS: I like to sprinkle salt across the top.
Cut into small squares while still warm, then let sit until cool.