Ingredients

1 cup unbleached all-purpose flour 

1/2 cup old-fashioned rolled oats 

1 teaspoon kosher salt 

1 stick (1/2 cup) cold unsalted butter, cut into small pieces 

3 ounces cream cheese 

1 large egg yolk 

2 tablespoons extra-virgin olive oil 

12 ounces Swiss chard, stems separated and sliced into 1/4-inch pieces 

1 large onion, sliced lengthwise 1/4 inch thick 

Kosher salt and freshly ground pepper 

3 tablespoons balsamic vinegar 

2 tablespoons golden raisins 

3 anchovy fillets, coarsely chopped (optional) 

2 tablespoons fresh thyme leaves 

6 ounces ricotta, room temperature 

1/4 cup finely grated Parmigiano-Reggiano 

3 tablespoons heavy cream 

1/2 teaspoon freshly grated nutmeg 

1 large egg yolk

Preparation

Crust: Pulse flour, oats, and salt in a food processor to combine. Add butter, cream cheese, and egg yolk; pulse until dough just holds together, 15 to 20 seconds.

Turn dough out onto a piece of plastic wrap and flatten into a disk; wrap in plastic. Refrigerate at least 1 hour or overnight.

Filling: In a large skillet, heat 1 tablespoon oil over medium. Add chard stems, onion, and a pinch of salt. Cook, stirring, until stems are soft and slightly brown, 8 to 10 minutes. Add vinegar and cook, stirring, until liquid is almost evaporated, about 2 minutes. Season with salt and pepper. Stir in raisins. Transfer mixture to a nonreactive bowl.

Heat remaining 1 tablespoon oil in same skillet over medium-high. Add anchovies, if using; cook, stirring frequently, 1 minute. Stir in thyme. Add chard leaves and cook until slightly wilted, about 1 minute. Season with salt and pepper.

In the bowl of a mixer fitted with the paddle attachment, beat both cheeses with 2 tablespoons cream until smooth, about 1 minute. Stir in nutmeg; season with salt and pepper.

Preheat oven to 375 degrees. On a large sheet of parchment, roll out dough to a 1/8-inch-thick round, about 15 inches in diameter. Arrange onion mixture evenly over dough, leaving a 3-inch border. Spread ricotta mixture over onion mixture; top with chard mixture. Fold edges of dough over and gently press down to seal. Transfer tart (still on parchment) to a baking sheet. Refrigerate 15 minutes.

In a small bowl, beat together egg yolk and remaining 1 tablespoon cream. Brush exposed dough with egg wash. Bake until crust is golden, 40 to 45 minutes. Serve warm or at room temperature.