Make gnocchi: Heat 1/2 tbsp. oil in a large pot over medium-high heat. Add half of spinach and a pinch each salt and pepper. Cook, tossing often, until barely wilted and still bright green, 2 to 3 minutes. Drain in a colander. Repeat with another 1/2 tbsp. oil, remaining spinach, and a pinch more of salt and pepper. Let cool in colander.
Gently squeeze excess liquid from cooled spinach. Chop 1/3 cup finely and set the rest aside.
Mix crab, chopped spinach, whole egg and yolk, chile flakes, and 1/4 tsp. each salt and pepper in a medium bowl. Add flour and mix thoroughly until it holds together like a soft dough.
Dip 2 small spoons (soup spoons are too big) in very hot water. Scoop 1 scant tbsp. dough with one spoon. Set second spoon upside down over dough and press firmly, then scoop underneath dough and onto second spoon. Repeat motion with first spoon. Scoop back and forth until you have a compact quenelle of dough. Alternatively, using wet hands to keep dough from sticking, and firmly roll it into scant 1-tbsp. balls. Set quenelles or balls on a baking sheet as you work, then chill while you make sauce.
Bring a large pot of lightly salted water to a boil. Meanwhile, make butter sauce: Cook wine, shallot, and garlic in a large frying pan over medium-low heat until wine has almost evaporated and shallot is softened, 3 to 5 minutes. Add cream and cook until simmering. Whisk in butter, a few cubes at a time, until melted and creamy. Whisk in salt, pepper, and fish sauce. Remove from heat to a warm spot. Let sit, whisking occasionally, until ready to serve, up to 30 minutes.
Reduce heat under boiling water to an active simmer. Drop in gnocchi and cook until they float, 3 to 4 minutes. With a slotted spoon, transfer to a plate. Meanwhile, reheat reserved spinach in a microwave.
Divide spinach among four plates. Top each with 6 to 8 gnocchi and drizzle generously with butter sauce. Serve with cheese hunk and a grater.
*Campbell likes smoky Controne hot pepper (find at markethallfoods.com) and salty, intense colatura (amazon.com).
Make ahead: Formed gnocchi, up to 1 day, chilled, or up to 2 months, frozen. (Freeze on baking sheet, then pop off and seal in a resealable plastic bag. Boil directly from the freezer, 5 to 6 minutes.) Spinach, up to 1 day, chilled. Butter sauce, up to 1 day, reheated in a bowl set over steaming water, whisking often.