To prepare ravioli, combine Homemade Ricotta Cheese, pecorino Romano, parsley, 1/8 teaspoon salt, and egg whites; mix with a fork until blended. Working with 1 gyoza skin at a time (cover remaining skins to prevent drying), spoon about 2 teaspoons ricotta mixture into center of skin. Moisten edges of skin with water; place 1 skin over filling, stretching slightly to meet edges of bottom skin. Press edges together with a fork to seal; place on a lightly floured baking sheet (cover with a damp towel to prevent drying). Repeat procedure with remaining skins and ricotta mixture to form 24 ravioli.
Bring 6 quarts water to a boil over medium-high heat. Add 4 ravioli; cook 5 minutes, turning ravioli carefully after 2 1/2 minutes. Remove ravioli from water with a slotted spoon; place on a platter. Repeat procedure with remaining ravioli; cover and keep warm. Reserve 1/2 cup cooking water.
To prepare topping, melt butter in a large nonstick skillet over medium heat; cook 3 minutes or until lightly browned, shaking pan occasionally. Add 1/4 cup reserved cooking water, asparagus, and 1/4 teaspoon salt; cook 3 minutes or until asparagus is crisp-tender and water evaporates. Stir in poppy seeds; cook 30 seconds. Add 1/4 cup reserved cooking water; cook over medium-high heat 1 minute or until liquid is reduced by about half. Add ravioli to skillet; toss gently to combine. Sprinkle with ricotta salata; serve immediately.