- 2 1/4 sticks unsalted butter, room temperature, plus more for pan
- 1 1/2 cups (6 ounces) pecans
- 1 cup (4 1/2 ounces) salted cashews
- 1 cup (5 ounces) salted peanuts
- 3/4 cup packed light-brown sugar
- 2 1/4 cups all-purpose flour
- 2 1/2 teaspoons plus a pinch of salt
- 4 cups granulated sugar
- 1/2 teaspoon cream of tartar
- 1 cup heavy cream
- Preheat oven to 350 degrees. Butter a 15-by-10-inch rimmed baking sheet, and line with parchment paper, leaving a 1-inch overhang on long sides; set aside. Spread nuts on another rimmed baking sheet. Toast until nuts are fragrant and lightly golden around the edges, about 10 minutes. Transfer nuts to a clean surface; spread evenly, and let cool completely. Coarsely chop, and set aside.
- In the bowl of an electric mixer fitted with the paddle attachment, beat 2 sticks of butter with the brown sugar on medium speed until light and fluffy, about 3 minutes, scraping down the sides of the bowl as needed. With mixer on low speed, add flour and a pinch of salt; mix until just combined.
- Transfer dough to prepared baking sheet, and cover with parchment paper. Using a wine bottle or small rolling pin, roll along the length of pan to smooth dough. (Alternatively, press the dough into the pan with the back of a large spoon.) Bake until lightly golden, 10 to 12 minutes. Transfer to a wire rack to cool completely.
- Combine granulated sugar, cream of tartar, remaining 2 1/2 teaspoons salt, and 1 cup
water in a wide, heavy-bottom saucepan. Cook over high heat, without stirring, until some sugar begins to melt and turn golden, 5 to 7 minutes. Reduce heat to medium; continue to cook, stirring occasionally with a wooden spoon, until sugar is completely melted, mixture is deep golden, and a candy thermometer registers 300 degrees (hard-crack stage). Stirring constantly, carefully pour cream slowly down the side of the pan (it will spatter) until fully combined. Remove from heat; add remaining 1/4 stick butter and stir
to combine.Transfer caramel to a heatproof bowl to cool for 10 minutes.
- Stir in nuts; spread caramel mixture over cooled crust. Bake until caramel is set, about 10 minutes. Transfer to a wire rack to cool. Cut into 3-by-2-inch bars. Bars can be kept in an airtight container at room temperature for up to 1 week.
For chocolate caramel-nut bars, follow instructions for caramel-nut bars, reducing salt in the caramel to 1 teaspoon and adding 8 ounces melted semisweet chocolate and 2 tablespoons Dutch-process cocoa powder to the caramel along with the 1/4 stick butter. Proceed with the recipe.