Double chocolate cookies

I've become famous for these around here. They're amazing! I found the original cookie recipe here, but with the added cocoa so that they're double chocolate. Yum!

½ c. butter
½ c. high-quality tub margarine (like Smart Balance)
¾ c. white sugar
1 c. brown sugar
2 eggs
1 tsp. vanilla
3 c. flour
¾ tsp. salt
¾ tsp. baking soda
1/3 c. cocoa
1 12-oz. bag chocolate chips (I use more chips than this. I also like to do half choc. chips, half peanut butter chips)

Cream together butter, margarine, sugars, eggs, and vanilla. In a separate bowl, sift together flour, salt, and baking soda. Add to creamed mixture and beat well. Mix in cocoa. Stir in chocolate chips .

Roll into balls and cook at 350 degrees. The original recipe says for 10-12 min. I think that the secret to making these AMAZING is to under-cook them slightly. When you take them out, they should look underdone. I usually let them sit on the cookie sheet for a couple of minutes (or until the puffiness falls), then immediately onto the cooling rack.