Preheat oven to 400°F; position rack in lower third of oven. Combine potatoes, 2 tablespoons of the salt, and enough cold water to cover by 1-inch in a large saucepan; bring to a boil over high, undisturbed. Reduce heat to medium; cook, undisturbed, until potatoes are very fork- tender, about 25 to 30 minutes. Drain well and pat dry.

Wrap the outside of a 9-inch springform pan with foil and generously brush sides and bottom of pan with 1 ½ tablespoons of the oil. Place drained potatoes in an even layer in pan; using a flat bottom measuring cup, smash potatoes firmly into the bottom, then press over bottom and about 2 to 2 ½-inches up sides of pan; crust should be about ¼-inch-thick on bottom and sides. Use a small offset spatula to evenly spread potatoes, smoothing and patching any holes or thin spots as needed and pushing upper edges into sides of pan. Brush potato crust evenly with 1 tablespoon of the oil; sprinkle evenly with 1 teaspoon of the salt.

Bake crust in preheated oven until edges are golden brown and slightly crisp and center is lightly golden, 35 to 40 minutes.

While crust bakes, heat remaining 2 tablespoons oil in a medium skillet over medium. Add shallot and cook, stirring often until softened, 2 to 3 minutes. Add spinach in batches, and cook, stirring often, until wilted, about 5 minutes. Remove from heat and add artichokes; stir until evenly combined. Remove from heat and transfer to a medium bowl; let cool completely, about 20 minutes. Pat dry with paper towels.

Remove pan from oven. Sprinkle half of the Monterey Jack (about 1 cup) in an even layer over bottom of potato crust.

Whisk together eggs in a large bowl until smooth. Add cream, creme fraiche, garlic powder, remaining 1 ½ teaspoons salt, and Parmigiano-Reggiano and whisk until smooth. Spread 1 ¾ cups of the spinach mixture over Monterey jack, and pour egg mixture over. Top decoratively with remaining ¾ cup spinach mixture, nestling some into eggs. Top with remaining 1 cup Monterey Jack, gently pushing some of the cheese into egg mixture and leaving some on top. Carefully transfer to oven.

Bake in preheated oven until filling is set, but still jiggly, and a thermometer inserted into the center registers 165°F, 45 to 55 minutes, loosely tenting with foil to prevent overbrowning, if needed. Let cool slightly on a wire rack, about 20 minutes. Run a knife or offset spatula around edge of quiche before removing from pan and let cool another 40 minutes to completely set before slicing.