Two Cups Flour

0 Line an 8x8 or 9x9 inch baking pan with parchment paper.
1 Place the unsalted butter, brown sugar, heavy cream, and vanilla into a medium sauce pan on medium-high heat.
2 Stir occasionally with a wooden spoon or spatula until the sugar and butter have melted. Allow the mixture to bubble in the center and small simmer. It should come to a full boil.
3 Add in the peanut butter and stir until smooth.
4 Remove pan from the heat.
5 Place the powdered sugar in the bowl of stand mixer with paddle attachment.
6 Carefully pour the hot mixture slowly onto the powdered sugar in the mixing bowl.
7 Tuen on the mixer to medium low mix a few spins. Then increase to medium  speed and mix until it resembles a thick cookie dough. Scrape the bottom of the bowl if needed. 
9 Transfer the warm fudge dough into the prepared pan. Take and offset spatula or your fingertips and level the fudge across the pan.
10 Place the chopped chocolate in a heat proof bowl. Melt the chocolate in the microwave in 30 second intervals, stirring in between each, for 90 seconds until smooth. Be careful not to overcook and burn the chocolate.
11 Pour the melted chocolate over the peanut butter fudge and level with an offset spatula. 
12 Let the chocolate cool for about 3-5 minutes, then sprinkle with flake sea salt. You can also add a half cup of chopped toasted nuts onto the chocolate at this time.
13 Cover the pan with aluminum foil and allow it to cool at room temperature for 3-4 hours. 
14 Once the fudge and chocolate have set, you can slice and package fudge for gifts.