Using a mixer, beat eggs and salt together in a large mixing bowl until frothy.
Add the sugar and beat 2 to 3 minutes. Add the vanilla and beat for another 30 seconds.
Place butter and unsweetened chocolate in a microwave safe bowl and microwave on high for 1 minute. Remove from the microwave and stir well. Microwave an additional 15 seconds if needed, and repeat again if needed.
With the mixer on, slowly pour chocolate and butter mixture into egg and sugar mixture. Add the flour and beat for 1 minute. Scrape down the sides of the bowl with a spatula, and beat mixture for an additional 30 seconds.
Line an 8x8 baking pan with foil or parchment paper. Lightly spray with nonstick cooking spray. Pour batter into pan. Place the pan on the top rack of the oven and bake 15 to 20 minutes until the center is barely set. You want these brownies to be slightly under cooked. Allow to cool completely.
Once brownies have cooled completely, but brownies in half with a knife, then cut each half into approximately 1/2" wide strips. Once cut, wrap all the brownies up in foil and place in the refrigerator for at least 30 minutes to chill.
When ready to top brownies with chocolate, chop and melt the semi-sweet or dark chocolate according to package directions. Dip each brownie "fry" into the chocolate and place it onto a baking sheet lined with either a silicone baking mat or parchment paper. Immediately sprinkle with sea salt. Repeat with remaining brownie fries. Place a baking sheet with brownie fries into the fridge to store. Serve cold.