Slowly melt the butter and the chocolate together on the oven or in a microwave safe bowl, over medium heat. In you choose to use the microwave use med power for 15-25 seconds at a time, stirring each time or you will burn them.
Combine the sugar, eggs and vanilla in a large bowl and whisk together well.
Sift all the dry ingredients into the egg/sugar mixture.
Add the melted chocolate and the mixture from step 2 and 3.
Add semi sweet morsels to the mixture and stir.
Pour the entire batter in prepared pan and bake in preheated 350 Degree F oven for 20-28 minutes or until a toothpick inserted into center produces a moist crumb.