Preheat your oven to 350 degrees F. Toast your pecans: If you want, take the time to toast your pecans a bit before they go in your bars. I like the extra flavor this adds, and your oven is preheating anyway, but it's not necessary. Spread 2 cups of pecans out onto a dry baking sheet and put it into the oven at 350. Stir the pecans every 2-5 minutes. Leave the pecans in the oven for 7-10 minutes total (How long it takes will depend on if they are already chopped.) When the pecans are fragrant and toasty, take them out and set aside to cool.

Make the shortbread: Line a 9x13 inch pan with parchment paper, or foil that you spray with nonstick spray. (You can also spray the pan itself no problem, but I like to be able to lift the bars out for easy slicing.)

In a large bowl or stand mixer, beat 1 cup of butter to within an inch of it's life. You want it to be light and fluffy, should take at least 2-3 minutes, plus breaks for scraping down the sides and bottom of the bowl.

Add 1/2 cup sugar and 1/3 cup brown sugar. Beat until the mixture is smooth and creamy, again making sure to scrape the sides and bottom of the bowl.

Add 1 and 1/2 teaspoons vanilla and 3/4 teaspoon kosher salt. Beat well.

Add 2 cups of flour. Beat it all in, it's going to feel like too much at first. Use your spatula to get the crumbs at the bottom if necessary. Don't over beat, once the flour is incorporated, stop mixing.

Transfer the mixture to the prepared 9x13 inch pan. I like to section out the dough into pieces and spread them over the bottom of the pan for easy pressing, see photos. Wet your hands just a little bit, and press the dough evenly into the pan. Don't form an edge crust, just press it all flat, wetting your hands again as necessary.

Bake the shortbread at 350 for 18-20 minutes, until lightly browned on the edges. Remove from the oven and set aside if your filling is not ready to go.

Make the pecan pie filling: Begin by browning your butter. This gives your bars that deep, nutty flavor that is so perfect for fall. In a small saucepan, add 1/2 cup butter. Turn the heat to medium and let the butter melt. Keep the heat on medium and don't walk away. Stir occasionally. Soon the butter will bubble and form a thick white foam on top. After that, the foam will recede a little bit and you will start to see little brown "bits" forming on the bottom of the pan. Stir them up and take a whiff. If you see brown specks and your butter has taken on a nutty aroma, your butter is browned. Take it off the heat right away. It goes from browned to burned real quick, so pay attention! Set aside to cool.

Meanwhile, scrape out any crumbs from the same bowl that you mixed your shortbread in. (It's Thanksgiving people, we don't have time for extra dishes!) Add 3 large eggs to the bowl and beat on medium speed for 3 minutes, until the eggs have lightened up in color a bit. (You're whipping air into them. Use a whisk attachment if you have one.)

Once the 3 eggs are well beaten, add 1/4 cup sugar, 1 cup brown sugar, 1/2 cup light corn syrup, and 1 tablespoon milk. Beat well.

When your butter has cooled a reasonable amount, add it to the egg mixture. If it is still pretty hot, you can tempt fate and add the hot butter while your mixer is running, to make sure you don't curdle the eggs. (That's what I always do. These are the kind of risks that make me feel like I'm living a dangerous life.) But if you're nervous, wait til you can stick your finger in the butter without it hurting. Beat the butter in well.

Add 1 and 1/2 teaspoons vanilla extract, 1/2 teaspoon kosher salt, 1 and 1/2 teaspoons fresh lemon juice (don't skip it! Lemon is the best secret ingredient to a great caramel sauce!), and 1 tablespoon flour. Beat it all together, whisking out any flour lumps.

If you haven't already, coarsely chop your pecans. Add the chopped pecans and 1/2 cup toffee bits to the egg mixture, and fold in with a spatula.

Pour the mixture on top of the baked crust. It's okay if the crust is still warm, even hot. Spread the mixture out evenly.

Bake the bars at 350 degrees F for about 30-35 minutes. When it is done, the edges of the bars will be light brown. The center of the bars may wiggle a little bit when you shake the pan, but it should not look sloshy. The bars from about 2 inches away from the edges and further out should not wobble. Your bars will bake a few minutes faster in a metal pan, a couple minutes slower in a glass pan.

Let cool completely to room temperature. I mean it now!

See notes for the best way to serve these pecan pie bars to your guests warm.

Serve with a scoop of vanilla ice cream and a drizzle of salted caramel! Totally unnecessary...but totally decadent.