Remove the butter from the refrigerator to soften for 30 minutes before you get started.
To toast the pistachios, heat nuts (whole) in a dry, heavy skillet over medium heat for 1 to 2 minutes or until they're golden brown and they give off a rich, toasty fragrance. ... Stir or toss the pistachios frequently for even toasting. Remove from pan to cool.
Preheat the oven to 350ºF.
Line 2 large baking trays with parchment paper and set aside.
Using a stand mixer with the paddle attachment, cream sugar and butter until light and fluffy; With the mixer on low speed, add the eggs, one at a time, beating well after each addition. Next, add the Limoncello and lemon extract, beating well. Slowly add dry ingredients; beating on low speed until combined. Add pistachios and zest and mix well.
For the first baking, turn the dough out onto the middle of one of the baking sheets and pat the dough into a 7" × 15" rectangle. Bake until golden and slightly firm, about 30 minutes then allow to cool.
Reduce the oven temperature to 325°F. Remove cooled biscotti from pan; cut diagonally into biscuits about 3/4 inch thick. Place the biscotti on the parchment paper-lined baking sheets. Bake for 10 minutes then turn over and bake for a further 10 minutes. Let cool completely before serving.
