Blettes panachées au fromage

• 3 pounds (1350 g) fresh Swiss chard
• 6 tablespoons (85

Butter the gratin dish well. Cut off the leafy part of the chard, wash, and drain. Trim away any bruised bits from the stems and peel them to remove all of the stringy surface. Slice the stems into strips about 1 inch (2½ cm) long and ¼ inch (⅔ cm) wide.

Cook the greens in a large quantity of rapidly boiling salted water for 3 to 4 minutes, until they are just tender. Remove with a skim