Pre-heat oven to 350 degrees F.
Place chocolate and butter in a microwave safe bowl and microwave on high for 30 seconds, stir, then microwave another 30 seconds, or until melted.
In a large bowl, whisk eggs, sugar and vanilla until well combined.
Slowly add the melted chocolate, whisking continually so you don't cook the eggs.
Finally, add the flour and baking powder and whisk until smooth. *See notes
Line a large, (12 X 17), sheet pan with parchment paper. Spray the paper lightly with cooking oil.
Spoon out approximately golf ball sized gobs of batter. A number 24 or number 30 cookie scoop makes it easy to measure. The cookies will spread a little in the oven.
Place in the oven on the center rack for 10 to 12 minutes, or until the cookies just start to crack, rotating the pan 180° after 6 minutes.
Remove from the oven and allow the cookies to firm up for about a minute before removing them from the pan with a turner. Place them on a wire rack to cool.