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1
Preheat oven to 350u00b0F.
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2
Arrange nuts in an even layer on a sheet pan.
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3
Toast nuts on middle rack of preheated oven just until they smell toasty and their color has deepened slightly, 7-9 minutes.
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4
Toasting the nuts before adding them to the filling ensures they stay crunchy.
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5
Set nuts aside and let cool, but leave oven on.
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6
Lightly grease a 9x13-inch baking pan with butter.
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7
Put butter, granulated sugar, and vanilla in a stand mixer bowl. Beat with a mixer on low speed to blend, then on medium-high speed until smooth and creamy. Add flour and salt on low speed and continue beating, scraping bowl as needed, until a soft dough forms.
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8
Using clean, slightly dampened hands, press dough into an even layer in bottom of the prepared sheet pan.
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9
Bake pan on middle rack of oven until crust is golden brown, 28-30 minutes. Remove from oven when done. While crust bakes, prepare filling.
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10
Roughly chop toasted nuts.
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11
Whisk together melted butter, brown sugar, maple syrup, eggs, vanilla, salt, and bourbon (if using) in a large mixing bowl until smooth and combined. Fold in chopped nuts.
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12
Pour filling evenly over the warm baked crust.
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13
Bake bars on middle rack of oven until nuts are golden brown and the center is no longer jiggly when gently shaken, about 30 minutes.
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14
Check to see that filling is done. Remove from oven or add time as needed.
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15
If you like, sprinkle bars lightly with flaky sea salt.
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16
Let bars cool about 30 minutes, then refrigerate at least 2 hours for filling to set.
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17
Slice and serve the cooled bars. Leftover bars may be stored in an airtight container at room temperature for 2 days, in the refrigerator for 5 days, or in the freezer for 3 months.
