In a skillet over medium heat, melt 2 tablespoons of unsalted butter. Add 2 cups of chopped pecans and toast for about 5 minutes, stirring continuously. Remove from heat and set aside to cool.

In a large saucepan, melt 2 sticks of unsalted butter over medium-high heat until it bubbles gently.

Add 1 cup of granulated sugar and 1 cup of packed brown sugar into the saucepan. Stir well until sugars dissolve completely.

Pour in 1-1/8 cups of heavy whipping cream, along with 1/4 teaspoon of salt and 1 tablespoon of vanilla extract. Stir until blended.

Increase heat until the mixture comes to a rolling boil. Begin timing for exactly 4 minutes, stirring occasionally.

After 4 minutes, remove from heat. Gradually stir in 4 cups of sifted powdered sugar until dissolved.

Gently fold in the toasted pecans until evenly distributed.

Pour the mixture into a baking dish lined with parchment paper and smooth the top. Sprinkle any remaining pecans on top.

Allow to set at room temperature for at least 3 hours or until firm. Cut into 1-inch squares.