Preheat your oven to 350°F. Spray a 9×13-inch baking pan with cooking spray or line it with parchment paper.

In a stand mixer or with a hand mixer, cream together the butter, peanut butter, and sugars on medium speed for about 2 minutes until fluffy.

Add the eggs and vanilla extract, and mix on medium for another minute.

Add the flour and salt, and mix on low until just combined (about 20 seconds).

Pour the batter into the prepared pan and smooth it out with a spatula to form an even layer.

Bake for 25-30 minutes until the center is set but still soft (this time is for a 9×13-inch metal pan; if using a glass or smaller pan, increase the baking time).

Let the bars cool to room temperature before topping with the ganache.

Place the chopped chocolate, butter, salt, and vanilla in a bowl. Set aside.

In a small pan over medium heat, heat the cream and sugar until hot but not boiling.

Pour the hot cream and sugar over the chocolate mixture and let it sit for 1 minute. Stir until smooth.

Set the ganache aside for about 15 minutes until it's pourable but still warm.

Pour the ganache over the cooled cookie bars. Place in the fridge until the ganache is set (firm enough to cut but not hard).

Cut into bars and sprinkle with flaky sea salt.