In large mixing bowl, combine butter, yogurt, melted chocolate and both sugars.
Add in eggs, and mix until well blended.
Add salt and baking soda to the wet mixture, and stir together.
Begin to add in the flour, doing a cup at a time until both cups are well incorporated.
Poor in chocolate chips and stir into the dough.
Using a non-stick 8" spring-form pan, line the bottom with parchment paper. (Place the pan on top of the paper, draw a circle around the outer base, and cut out to fit exactly).
Drop in (by spoon-fulls) 1/2 or less of the cookie dough, and, with your hands, press down to make an even layer at the bottom of the pan.
Put in oven for 25-30 minutes (depending on your oven's temp), and bring out to cool, once at desired doneness.
Once cooled, remove giant cookie from pan, wrap in plastic wrap (to prevent dryness).
Repeat above directions and make 1 more giant cookie.
Once second cookie comes out to cool, place ice cream on counter to soften a little.
Leaving the cooled cookie in the spring-form pan, empty entire pint of ice cream into pan on top of the cookie.
Spread ice cream evenly over cookie.
Unwrap first cookie, and place it on top of the ice cream (I do it face down, so that the top is very flat and even. It makes for easier decorating).
Push cookie down until everything is compacted and firm, cover with plastic wrap, and place back in the freezer.
Now -- to DECORATE this cake -- the possibilities are endless. You can use powdered sugar to dust the top then drizzle melted chocolate over that, or check out kittencal's great recipe for frosting in my "baking treats" cookbook for some real fun! Also and idea -- add shaved chocolate to the sides. I just left mine plain, but it would add a bit of sophistication, I think.