Start by mixing up the dough. If you have a marble slab to work on, that would make clean up easier. Pour the flour into a mound, and create a well in the middle. Crack two eggs into the center. Use a fork to whisk the eggs, slowly incorporating more and more flour. After about a minute, add the remaining eggs. Use a fork to continue folding in more flour. Eventually, it will make more sense to use your hands. Pull the dough out of the flour, and knead it, slowly adding more an more flour.
I am going to be honest, this is hard. It's a work out. You will need to knead and knead until you can eventually incorporate all the flour. Or you can skip this step by using lasagna sheets instead.
Once you have a ball of dough, cover it with plastic wrap, making sure that there is no air between the plastic wrap and the dough. Set the dough aside.
Then get to work on the filling. Squeeze all of the water out of the spinach. Then combine the spinach, ricotta, parmesan, nutmeg, salt, and pepper in a food processor. Mix until smooth.
Now it's time to roll out your dough. I used a rolling pin to roll the dough out as much as I possibly could, until the dough was thin. I rotated the dough clockwise as I rolled it.
To make the plin either use a piping bag or a spoon to place a small ball of filling on the edge of the dough. You want the filling to be the size of a hazelnut. Line the filling up on one edge of the dough, making sure you space it out so you can fit a finger between. Then fold the dough with the filling in to over, pinch the plin together, and cut with a pastry cutter. Watch the video - I explain what to do. It's a more visual thing, it would be hard to explain in words alone.
Continue making plin, using up all the dough and filling.
Then bring a pot of salt water to a boil, add the plin and cook until they float.
While the plin cook, prepare the sauce. Melt the butter in a saucepan. As soon as the butter begins to darken, add the sage. Stir the butter, submerging the sage, and letting it cook until the leaves are crisp and the butter has browned.
Drain the plin, and drizzle the butter and sage over.