- For Base:
- 2 cups (about 10 ounces) all-purpose flour
- 1/2 teaspoon baking powder
- 1/2 teaspoon kosher salt
- 3/4 cup unsalted butter, at room temperature
- 1 cup (about 7 ounces) sugar
- 1 large egg
- 3/4 teaspoon vanilla extract
- For Topping:
- 1 1/2 cups (about 10 1/2 ounces) sugar
- 1 cup heavy cream
- 6 tablespoons unsalted butter, roughly cut into pieces
- 1 teaspoon vanilla
- 1/2 teaspoon salt
- 2 cups salted roasted cashews
Adjust oven rack to middle position and preheat oven to 375°F. Line a 13- by 9-inch baking pan with foil. Grease foil with butter. In a small bowl, combine flour, baking powder, and salt; set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat together butter and sugar until fluffy and light in color, about 4-5 minutes. Beat in egg, then vanilla. Beat in the flour mixture in two additions, scraping down the sides of the bowl each time.
Place dough in prepared pan. Using either floured hands or a piece of plastic wrap, press dough evenly into the bottom of the greased baking pan. Let chill in refrigerator for 20 minutes.
Bake crust until golden brown, about 30 minutes. Remove crust, but keep oven on. Let crust cool completely. While crust is cooling, make filling.
Place sugar in a nonstick saucepan over medium high heat. Let stand until bottom layer of sugar begins to melt, then start stirring, continuing to stir until sugar has turned light brown in color and smooth in texture. Pour in heavy cream, being careful of it splattering. Stir constantly until mixture is smooth again, about 5 minutes. Turn down heat and stir in butter, vanilla, and salt. Take mixture off heat and stir in cashews. Pour mixture into pan. Bake for 15 minutes.
Let mixture cool for at least two hours or until set. When firm to the touch, cut into bars. Bars can be kept in the refrigerator for easier cutting.