We were inspired by the flavors of pecan pie when we created these treats. They're simple to make, thanks to a quick crust and stovetop filling. You can use peanuts, walnuts, or pecans in place of hazelnuts.
Preheat oven to 375 degrees. Line an 8-inch square baking pan with parchment, leaving a 2-inch overhang on all sides; butter parchment. In a large bowl, using a mixer, beat 1 stick butter and 1/3 cup brown sugar on medium-high until light, 1 to 2 minutes. Add flour and 1/4 teaspoon salt and beat on low until combined. Increase speed to medium and beat until clumps form. Press dough evenly into pan. Bake until golden and dry, about 20 minutes. Let cool 15 minutes. Reduce temperature to 325 degrees.
In a medium saucepan, combine corn syrup, cream, 1/4 teaspoon salt, and remaining stick butter and 2/3 cup brown sugar. Bring to a boil and cook 1 minute. Stir in nuts, then pour over crust.
Bake until bubbling in center, about 15 minutes. Sprinkle with chocolate, if desired. Let cool 1 hour. Using parchment, lift out of pan and refrigerate until set, 1 hour. Cut into 24 pieces. (Store in an airtight container, up to 2 days.)
These bars travel well, so they are great to bring to a potluck Thanksgiving or other fall gathering.