Wash your potatoes and then bring them to a boil with the kosher salt in a 4 quart pot filled with enough water to cover. Boil until fork tender. Drain the potatoes and allow them to cool until you can handle them, about 10 minutes. Remove the skins from the potatoes and then pass through a food mill. Add the butter and stir until the butter is completely melted. Salt to taste.
On a 9 x 13 sheet pan, flatten the mashed potatoes with a fork, spreading them out evenly. Mash in the egg, yolk, and the pepper. Whisk flours together in a separate bowl. In tablespoon increments, sprinkle the flour over the potatoes and work in with the fork. By the third addition, you should be kneading the dough by hand. Season the dough to taste with salt.
Dust the counter with glutinous rice flour and knead the dough to smooth and it is not sticky. Divide the dough into eight sections and then roll each section into ropes 2 feet long and ½ inch thick. Cut each rope into equal sized segments, 1/2 – inch, and then roll each segment into a ball. Roll each segment with your gnocchi roller, or down the tines of a fork to texturize the exterior of the pasta. This will trap the sauce and give the gnocchi just the right texture when cooking. Repeat until all the gnocchi are formed. Bring a pot of heavily salted water to a boil. Using a spatula, carefully lower the gnocchi into the water. Boil until the gnocchi are puffed up and tender. They are done when they float and have boiled for a full minute.
If you are not cooking the gnocchi right away, cover tightly and refrigerate for up to 1 day before using. Freeze in an airtight container for up to three weeks.
Makes 150 gnocchi.
If you have some left over mashed Yukon gold potatoes, they work well for this recipe, too, just make sure you refrigerate the gnocchi for 2 hours before cooking.
Melt the butter in a saucepan. The moment you can no longer see any milk fats, begin swirling the pan over the flame to brown the butter. When you see brown flecks over the bottom of the pan, swirl for 30 seconds longer, add the water and remove from the heat. Blend with a wand mixer until emulsified. Pour over gnocchi and serve with Parmesan and fresh sage.