For the filling:
Cover potato (skin on) with cold water in a small pot and set over a medium-high heat. Cook until tender, about 30 minutes. Remove the potato from water and allow to cool just slightly. Using a spoon (or your hands while wearing gloves), remove the skin from the potato and push through a ricer. Allow to cool.
Remove the rind from the robiola and allow to temper slightly (so that it's easier to mix). Finely mince chives and place in a medium bowl. Add the robiola and riced potatoes. Season with salt, pepper, and olive oil. Add just enough milk to the mixture so that it mixes smoothly.
basic pasta dough. Cut the pasta dough into 3 equally sized pieces. Re-wrap 2 of the pieces in plastic wrap and set aside. Begin working with the 1 unwrapped piece of dough. On a lightly floured work surface, use a floured rolling pin to roll out the pasta dough until it is 1/8-inch thick (you can also use a pasta machine and roll out the dough on its thinnest setting).
Lay the resulting pasta sheet on a lightly floured surface with the long side facing you. Trim the edges so they are straight. Using a tablespoon, scoop equally sized spoonfuls of the filling and place along the bottom half of the pasta sheet, leaving a 1½ inch border of dough at the bottom and sides: each dollop of filling should be approximately 1½ inches away from the next. Pull the top edge of the pasta up and over the filling. The dough should form 1 large pocket over the dollops of filling. Seal the agnolotti by gently molding the pasta over the filling and pressing lightly with your index finger to seal the edge of the dough to the pasta sheet. Do not drag your finger along the dough to seal, or you risk ripping the dough. When it is sealed, there should be about ½ inch of excess dough visible along the bottom of the mounds of filling (where you sealed it). Be certain that you are sealing tightly while pressing out any pockets of air. Seal the left and right ends of the dough.
To shape agnolotti: Starting at 1 end of the dough, place the thumb and forefinger of each hand together as if you were going to pinch something and, leaving about 1 inch of space between your hands and holding your fingers vertically, pinch the filling in 1 inch increments, making about ¾ inch of "pinched" are between each pocket of filling. It is important to leave this much "pinched" area between the agnolotti, or when the agnolotti are separated, they may come unsealed. Run a sharp knife or crimped pastry wheel along the bottom edge of the folded-over dough, separating the strip of filled pockets from the remainder of the pasta sheet. Do not cut too close to the filling, or you risk breaking the seal. Separate the individual agnolotti by cutting the center of each pinched area, rolling the pastry wheel away from you. Working quickly, place the agnolotti on a baking sheet dusted with a thin layer of cornmeal, which will help prevent sticking. Don't let the agnolotti touch each other, or they may stick together.
Add the agnolotti to salted boiling water and allow to cook for 4-5 minutes.
Add the butter to a cold pan and place over medium heat, stirring occasionally. The butter will begin to foam, then the foam will subside. Allow the butter to cook, stirring frequently until it seperates and the small bits of milk fat begin to caramelize. In about five minutes, the butter will begin to take on a nutty aroma. Remove agnolotti from the pasta water, taking care to shake almost all of the water off. Add pasta to brown butter and toss quickly.
Plate and finish with raschera cheese. Top with chopped hazelnuts and serve.