Place the softened butter and sugar into a large mixing bowl. Use a mixer to beat the butter and sugar together until fluffy and creamy, about 4 to 5 minutes.
Next, add in the vanilla extract, then add one egg at a time, mixing well after each addition. After adding all three eggs, continue mixing for 1 minute until the batter is smooth.
In a separate bowl, combine the dry ingredients: all-purpose flour, baking powder, and salt.
Add the dry ingredients into the wet batter in thirds, mixing well after each addition until the batter is smooth.
Use a spatula to mix in the final third portion of the flour by hand; the cookie dough will be thick and just slightly sticky. Fold in the chopped pistachios last.
Turn the cookie dough out onto the lined baking sheet. Shape the dough first into a long log, then gently press and shape the dough into a 7x11-inch (approximately) rectangle. Use the SmartGrid lines on Reynolds Kitchens® Parchment Paper with Stay Flat Dispensing Packaging to create an even shape.
Baking the Biscotti:
Bake the cookie sheet at 350°F for 25 to 27 minutes, until the top and edges are lightly browned.
Remove the cookie sheet from the oven, cool for 7 to 8 minutes, then gently transfer onto a cutting board. Using a long, serrated knife, cut the sheet vertically into cookies, about 1-inch thickness.
Carefully transfer the cut cookies back onto the lined baking sheet, spacing the cookies at least 1-inch apart.
Reduce the oven temperature down to 290°F and bake the cookies for an additional 50 to 60 minutes, until the cookies are golden brown and crispy.
Remove the cookies from the oven and allow them to cool.
Adding the Chocolate:
Optional: take an extra step and dip the cookies into chocolate. Place the chocolate melts into a microwave-safe bowl and heat the chocolate in 1-minute intervals, stirring until the chocolate is melted and smooth.