Preheat oven to 425°
Whisk eggs with sour cream, salt, pepper, and chives in a large bowl until smooth. Fold in the parmesan cheese and set aside.
Heat a 10” ovenproof skillet over medium high heat. Add the butter and melt until it foams. Add the shallots/onions and cook, stirring occasionally, until soft and the edges start to brown, 4-5 minutes.
Add asparagus, toss to coat in the fat, and sautee 3 minutes, stirring occasionally.
Pour the egg mixture into the skillet, then gently shake the skillet to evenly distribute. Continue cooking over medium heat until the edges are firm, 3 minutes.
Transfer the skillet to the oven. Bake until the the eggs are puffed but the center is just slightly soft (it will have a slight jiggle to it), 12-14 minutes.
Remove the skillet from the oven using oven mitts and place it on a cooling rack. Cool at least 5 minutes, or until the edges gently pull from the sides of the skillet.