Preheat oven to 325°F. Using a stand mixer with paddle attachment, cream butter, sugar, and salt. Add egg and mix until combined. Add flour and mix until combined. Dough will be tacky.

Line a quarter-sheet pan (about 9- by 13-inch) with parchment, leaving 1-inch overhang on both long edges. With floured hands, press dough into pan and smooth top with the flat bottom of a measuring cup. Prick surface with fork. Bake for 30–40 minutes, until edges begin to turn golden and the center is firm.

Increase the oven temperature to 375°F.

In a heavy saucepan over medium heat, melt butter with sugars, honey, and salt, stirring to combine. Cook until the caramel reaches 257°F (hard ball), which won't take long. Remove from heat and stir in the heavy cream then add the chopped pecans.

Dollop the pecan caramel over the baked shortbread crust and smooth to an even layer. Bake 10 minutes until caramel is bubbly at the edges. Transfer to a rack to cool completely before cutting.

To cut: lift slab using the parchment edges and transfer to a baking board. Trim edges with a sharp chef's knife then cut as desired.