01 -
Preheat the oven to 350°F (175°C) with a rack set in the middle. Spray the bottom and sides of a 9x9-inch square baking pan with non-stick baking spray. Line the bottom and up two sides of the pan with parchment paper, leaving about 1 inch overhanging at the top of each side. Lightly spray the parchment with baking spray and rub with a paper towel.
02 -
Combine the soft butter, sugar and vanilla in a medium-large bowl. Stir well with a silicone spatula or wooden spoon to combine. Add the salt and stir again. Add the flour and stir until all the flour is incorporated, scraping the sides of the bowl as you go. The dough will be crumbly, but ensure all flour is mixed in.
03 -
Spread the crumbs across the bottom of the prepared pan and press them into an even layer with lightly floured hands. Bake on the middle rack for 22-25 minutes, or until light golden brown. Transfer the pan to a cooling rack. Increase the oven temperature to 425°F (220°C).
04 -
Towards the end of the shortbread baking time, start making the caramel/almond topping. In a medium-size microwave-safe measuring cup or bowl, combine the cream, honey, vanilla and butter. Microwave on high power for 2 minutes. Set aside.
05 -
In a heavy medium-sized saucepan, combine the sugar, water and corn syrup and bring to a boil over moderately high heat, stirring just to combine. Don't stir after this. Cook the syrup over moderately high heat, swirling the pan occasionally, until a medium amber caramel forms, about 8-10 minutes. (Watch the syrup carefully the last couple minutes, swirling the pan more frequently to prevent burning). Remove from the heat.
06 -
Carefully add the honey/cream mixture (it will bubble furiously) and stir to combine. Return the pan to the burner and cook the caramel over moderately high heat, stirring frequently until a candy thermometer registers 255°F (124°C), about 7-10 minutes. Stir in the almonds and immediately pour the caramel mixture over the shortbread, spreading to an even layer.
07 -
Return the pan to the oven and bake for 7-10 minutes, or until the topping is bubbling all over and a nice deep golden brown. Transfer the pan to a cooling rack and sprinkle with flaky sea salt, if desired. Allow to cool completely before cutting, at least 2 hours.
08 -
Run a thin-bladed knife along the two edges of the pan that do not have parchment to loosen the shortbread. Pull up on the parchment paper and transfer the shortbread to a cutting board. Using a sharp, heavy knife, cut the pastry into desired size squares.