Preheat oven to 425°F/220°C. Wash and dry the potatoes. Pierce the potatoes all over with a fork. Place them on a baking pan and bake for 40 to 50 minutes or until tender when pierced with a sharp knife, allow to cool.
Once the potatoes are cool enough to handle, the skins should peel off easily. Add the potato to a bowl. Mash the potatoes well, or run through a potato ricer or food mill. Add the ricotta, Parmesan cheese, nutmeg, salt and pepper. Use a fork to lightly mix well.
Turn the potato mix onto a floured surface and use your hands to mix a little flour. Knead the dough and add more flour as needed just until it holds together and is not sticky. The amount of flour needed will depend on how much moisture is in the mixture.
Take a golf ball size piece of dough and roll out into a long cigar shape, ¾ inch (2 ½ cm) thick. The dough will be delicate, if it breaks, just roll it back together and do it again. Cut 1 inch (3 cm) pieces using a pastry cutter or knife.
Take each piece and roll over a gnocchi board or the back of a fork to create ridges and put them back onto the floured board in an even layer, not touching if possible. Repeat until all of the gnocchi are rolled. If you are freezing them, put the board of gnocchi into the freezer and freeze for 1 hour (this way they will freeze without sticking together) then add them to a freezer bag or container with a lid.
To a large frying pan, melt the butter over medium heat. When the butter is bubbly, add the fresh sage and cook until crispy, about 1-2 minutes. Remove the sage and drain on a paper towel.
Add the gnocchi to the same butter and swirl the pan to coat them with the butter. Cook for 2 minutes on the first side until brown and crispy, turn. Cook for 2 more minutes until crispy. Be gentle so they don’t break.
Serve warm and top with the browned butter they were cooked in and the crispy sage along with the marinara/tomato sauce and top with shaved or grated Parmesan cheese.