Caramel-Nut Bars

Directions

1. 1
   Preheat the oven to 350F.
2. 2
   Butter a 15-by-10-inch rimmed baking sheet, and line with parchment paper, leaving a 1-inch overhang on long sides; set aside.
3. 3
   Spread nuts on another rimmed baking sheet.
4. 4
   Toast until nuts are fragrant and lightly golden around the edges, about 10 minutes.
5. 5
   Transfer nuts to a clean surface; spread evenly, and let cool completely.
6. 6
   Coarsely chop, and set aside.
7. 7
   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.
8. 8
   With mixer on low speed, add flour and a pinch of salt; mix until just combined.
9. 9
   Transfer dough to prepared baking sheet, and cover with parchment paper.
10. 10
    Using a wine bottle or small rolling pin, roll along the length of pan to smooth dough.
11. 11
    (Alternatively, press the dough into the pan with the back of a large spoon.)
12. 12
    Bake until lightly golden, 10 to 12 minutes.
13. 13
    Transfer to a wire rack to cool completely.
14. 14
    Combine granulated sugar, cream of tartar, remaining 2 1/2 teaspoons salt, and 1 cup water in a wide, heavy-bottom saucepan.
15. 15
    Cook over high heat, without stirring, until some sugar begins to melt and turn golden, 5 to 7 minutes.
16. 16
    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 300F (hard-crack stage).
17. 17
    Stirring constantly, carefully pour cream slowly down the side of the pan (it will spatter) until fully combined.
18. 18
    Remove from heat; add remaining 1/4 stick butter and stir to combine.
19. 19
    Transfer caramel to a heatproof bowl to cool for 10 minutes.
20. 20
    Stir in nuts; spread caramel mixture over cooled crust.
21. 21
    Bake until caramel is set, about 10 minutes.
22. 22
    Transfer to a wire rack to cool.
23. 23
    Cut into 3-by-2-inch bars.
24. 24
    Bars can be kept in an airtight container at room temperature for up to 1 week.
25. 25
    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.
26. 26
    Proceed with the recipe.
27. 27
    A combination of salted nuts is stirred into a bowl of freshly cooked caramel.
28. 28
    The caramel-nut mixture is spread atop a cooled cookie base before the bars are baked a second time to set.