Melt the butter in a pan on the stove.
Stir in the brown sugar. Remove from the stove, and let it cool for ten minutes.
Add the eggs, one at a time, beating each egg before adding it, and beating after each one.
Whisk the flour, baking powder, and salt.
Stir flour mixture into the pan, and mix well -- it is thick.
Add chocolate bits, stir until distributed evenly.
Spread in a large buttered 15" x 10" pan.Or line the pan with parchment paper before spreading. Bake at 350°F for 25-30 minutes.
Cool, and cut into bars.