Place the ricotta in a fine-mesh sieve over a bowl and let it drain for 15 minutes to remove excess moisture.
In a medium bowl, combine the strained ricotta, egg white, grated parmesan, sea salt, and black pepper until smooth.
Gently fold in the all-purpose flour until a soft, slightly tacky dough forms, being careful not to overwork it.
Turn the dough onto a lightly floured surface, divide into four pieces, and roll each into a long rope about 1/2-inch thick.
Cut the ropes into 1-inch pieces and lightly indent each with the back of a fork for a classic texture.
Bring a large pot of salted water to a gentle boil and cook the gnocchi in batches until they float to the surface, about 2-3 minutes.
While the gnocchi cook, melt the butter in a large skillet over medium heat and add the minced sage and lemon zest.
Use a slotted spoon to transfer the gnocchi directly from the water to the skillet, tossing gently to coat.
Stir in the lemon juice and fresh parsley, then pan-sear for 1 minute until the edges are slightly golden and fragrant.