Slice through the chard leaves a few times.
Dice the ribs.
Heat the olive oil and cook the onion until soft.
Add the ribs and cook until tender, then add the leaves in batches and cover to wilt.
Heat the oven to 400°F/200ºC.
Spread half the greens in a baking dish.
Pour over half the béchamel.
Put the remaining chard on top, then the remaining sauce.
Sprinkle over the cheese.
Bake until hot through and golden on top.
*Good with cooked chopped ham through it, too.
*For a richer dish, stir grated gruyere or comté into the hot béchamel until it melts.
* You can also blanch the chard stems in boiling salted water until tender, then drain and rinse immediately in ice-cold water. Drain again and they're ready to use in gratin. The leaves may be blanched in the same water, squeezed dry, then chopped for the gratin
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