Galette: SAVORY FILLING

Name: Galette: SAVORY FILLING
Cuisine: European
Ingredients: One bunch (or about 4-5 large stalks) of Swiss chard, leaves separated from stems; 1 Onion; 1 tablespoon Balsamic vinegar; 2 Anchovies (optional); 1 pinch Nutmeg; 1 teaspoon thyme; 1 cup Ricotta; ½ cup Heavy cream (for filling and wash); ½ cup finely shredded Parmigiano cheese; 2 Garlic cloves; ½ teaspoon Black pepper; ½ teaspoon Kosher salt; 1 Egg yolk; zest of one lemon