A creamy cremini-mushroom filling awaits inside these savory packages, suitable as a side dish or vegetarian main course at any holiday table.
Reserve 6 longest chard stems; thinly slice remaining stems (you should have 2 cups).
Melt butter in a large skillet over medium-high. Add shallots and mushrooms and cook, stirring occasionally, until softened, 8 to 10 minutes.
Add sliced chard stems; season with salt and pepper. Cook until tender, stirring frequently, about 1 minute. Stir in cheese, creme fraiche, and eggs.
Prepare a large ice-water bath. Blanch chard leaves and reserved stems in a pot of boiling water until just tender and color brightens, about 2 minutes. Transfer to ice bath to cool; drain on kitchen towels.
For each bundle, place 1/4 cup mushroom mixture on a chard leaf. Fold sides in toward middle; roll up. Thinly slice each blanched chard stem into 4 pieces; use 2 to tie each bundle.
In batches, arrange bundles, seam-sides down, in a single layer in a steamer basket set in a pan of simmering water. Cover and steam until warmed through, 6 to 8 minutes a batch; serve.