Weigh or measure the flour, baking powder, salt, and ginger into a bowl. Run a whisk through to blend, then set aside. In another small bowl, weigh or measure the powdered sugar and set aside. Next, zest and juice the lemons, keeping the zest and juice in separate containers.
In a stand or handheld mixer bowl, cube the butter. On a medium speed cream the butter for 1–2 minutes. Reduce the speed to low and slowly add the powdered sugar. Increase to medium and mix for about 3 minutes. Scrape down the sides and finish blending the sugar into the butter. Add the lemon juice and zest, mixing until incorporated.
Reduce the speed again and add the flour mixture about a ½ at a time. Stop the mixer, scrape down the sides and across the bottom, then add the hazelnuts. Mix on low for about 15 seconds, just until the hazelnuts are evenly distributed throughout the dough.
Transfer the dough from the bowl onto a hard surface or pastry mat lightly dusted with powdered sugar. Check to make sure all the flour has been incorporated. I use a baguette pan to help keep the roll round during chilling, so I shape the roll to about 17–18 inches in length. Wrap the log in plastic wrap and refrigerate for at least 45 minutes or overnight.
Preheat the oven to 350°F (175°C or 180°C) and line two cookie sheets with parchment paper; set aside. Remove the log from the refrigerator, unwrap the plastic wrap, and score it every ¾ inch to ensure evenly sized cookies. Now using a sharp knife slice the cookies and add 12 or 13 to a pan. They do not spread much when baking, so you should be able to fit all the cookies on two pans. Bake for 12–14 minutes, then transfer to a cooling rack. Once cooled, sprinkle with powdered sugar.