Preheat oven to 375°F.
On Medium heat, melt butter in a medium sauce pan. Once melted, reduce heat to low and add unsweetened chocolate. Wisk constantly until chocolate is smooth. (Reduce heat or lift pot above burner if it is melting too quickly or starting to burn).
Remove sauce pan from the stove. Add sugar, coffee, vanilla, and salt. Wisk.
Add eggs, one at a time, wisking after each addition until the batter is smooth.
Add flour and chocolate chips to the batter, stir until combined.
Spread batter evenly in a 9 by 14 glass baking pan and bake in middle of the oven for 25-28 minutes.
Allow to cool for at least 15 minutes before cutting. Cut into as many squares as you would like -- don't cut too small -- 15-20 squares work best.
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