Preheat the oven to 375°F. Lightly butter a shallow a 1 ½ quart baking dish, or spray with nonstick cooking spray.
In a food processor, pulse the garlic and Swiss chard until chopped. Add the olive oil and puree until combined.
In a large bowl whisk together the cream, minced chard mixture, salt and pepper, and ½ cup of the Gruyere. Add the pattypan squash and use a large spoon or your hands to combine until the squash is all well coated with the cream mixture. Turn the squash into the prepared baking pan. Sprinkle the remaining ½ cup grated cheese on top.
Bake for about 35 minutes until the cheese is nicely browned and the casserole is bubbling around the edges. Let sit for about 5 minutes then serve hot.
Notes
You can use green or yellow pattypan squash, it doesn’t matter a bit. Sometimes they are called baby summer squash. In any case they are about 1 inch in diameter, with tiny ruffled edges, and they are adorable. Trim off and tiny stems and root ends, but just barely so you don’t lose much of the already diminutive vegetable.