In the bowl of a stand mixer (or using a hand mixer), beat the butter, powdered sugar, and brown sugar together. Beat for about 3 minutes, or until the mixture is well-incorporated and smooth.

Add the vanilla extract and kosher salt. Mix until just combined. Add 1 cup of flour, and mix on medium-low speed until well-combined.

Add the remaining cup of flour and mix on medium speed. This will look like it is too floury at first, but it will combine if you keep mixing. When the dough forms and pulls away from the sides of the bowl, it is ready for the next step.

Add the pecans and toffee bits to the mixing bowl, and mix those in. Remove the dough from the bowl, divide it into 2 equal-sized pieces, and roll each piece into an 8-inch long log about 2 inches wide.

Wrap the dough in plastic wrap and let it chill in the refrigerator for at least 1 hour.

Preheat the oven to 350°F and line a sheet pan with parchment paper.

Take your cookie dough out of the refrigerator, and cut each log into 14 or 15 slices.

Place the slices of dough on your prepared baking sheet, leaving about ½ inch between cookies. (These cookies won’t spread too much while baking, so don’t worry about leaving a large amount of space.)

Bake for 12 - 15 minutes, or until the sides of the cookies start to brown.

Remove from the oven, let cool on the sheet pan, and roll in powdered sugar if desired.