Rainbow-Chard Quiche

Name: Rainbow-Chard Quiche
Prep time: 45 min
Total time: 45 min
Cuisine: European, Mediterranean, French
Ingredients: 1 stick unsalted butter; 1 small onion, chopped (1 cup); 1 bunch rainbow Swiss chard (14 ounces), leaves coarsely chopped, stems cut into 1-inch pieces; Coarse salt and freshly ground pepper; 12 phyllo sheets, thawed, each trimmed to an 11-inch square; 10 large eggs, room temperature; 1.25 cups whole milk; 0.75 cup heavy cream; 1 tablespoon Dijon mustard; 0.25 teaspoon freshly grated nutmeg; 0.5 cup sour cream; 3 tablespoons harissa (available at kalustyans.com)