buckwheat crêpe batter, half only (https://coertvonk.com/1673.recipe)
crème fraîche, (or sour cream)
Preheat oven to 200 °F (85 °C).
Discard coarse stems from spinach. Wash leaves well and drain in a colander. In a large heavy kettle steam spinach with water clinging to leaves, covered, over moderate heat, stirring occasionally, until wilted, about 3 minutes.
Drain spinach in colander, pressing out as much liquid as possible with back of a large spoon. Return spinach to kettle and cook in butter with salt and pepper to taste, uncovered, over moderate heat, stirring, 30 seconds.
Brush a 12" non-stick skillet lightly with oil and heat over moderately high heat until hot but not smoking. Remove skillet from heat. Working quickly, stir batter and fill a 1/4-cup measure. Pour batter into skillet, tilting and rotating skillet quickly to cover bottom.
Cook crêpe over moderately high heat until bottom is golden and top appears almost dry, about 1 minute. Turn crêpe over and put one-fourth spinach in center. Fold in edge of crêpe to form a square, leaving spinach in center exposed, and cook crêpe 30 seconds, or until bottom is golden. Slide crêpe onto a large baking sheet.
Keep crêpe warm in oven while making 3 more crêpes with remaining batter and spinach in same manner.
Brush skillet lightly with oil and heat over moderate heat until hot but not smoking. Break eggs, 1 at a time, into skillet and cook until whites are set, about 2 minutes.
Top each crêpe with an egg and 1 tablespoon crème fraîche or sour cream.