Preheat the oven to 350 degrees F. Place the pecans on a sheet pan in a single layer. Toast for 5 -10 minutes, stirring once or twice for even toasting.
Line an 8×8 baking dish with parchment paper leaving extra hanging over the edges. This will help with removing the fudge from the baking pan.
Combine the butter, granulated sugar, brown sugar, heavy cream, and kosher salt in a large heavy-bottomed saucepan over medium-high heat. Bring to a boil.
Boil (full rolling boil not simmer) for a full 4 minutes, stirring constantly. Remove from the heat.
Carefully pour the very hot mixture into a large mixing bowl, add the vanilla extract and the powdered sugar. Beat the mixture until creamy and smooth.
Stir in 1 3/4 cups of the toasted pecans, reserving 1/4 cup for the top.
Pour into the prepared baking pan. Sprinkle reserved pecan pieces evenly over the top of the fudge. Press in slightly using a piece of parchment paper.
Let cool to room temperature. Then refrigerate for 3-4 hours or until firm. I do this overnight for the flavors to really combine.
Before cutting into your desired size pieces let it come to almost room temperature. If it’s too cold it will start breaking into bits. We did five cuts horizontally and 5 cuts vertically.