Chanterelle and Gruyère Tart

Name: Chanterelle and Gruyère Tart
Cuisine: European, Mediterranean, French
Ingredients: 1 sheet frozen puff pastry ((half of 17.3-ounce package), thawed); 1 large egg yolk (, beaten to blend with 1 teaspoon water (for glaze)); 2 tablespoons unsalted butter; 3 garlic cloves (, minced); 1/4 teaspoon salt; 1/4 teaspoon pepper; 2 teaspoons fresh thyme leaves; 2 tablespoons flour; 3/4 cup half and half; 1 tablespoon butter; 1/4 cup thinly sliced shallots; 1 1/2 pounds fresh chanterelle mushrooms; 1/2 cup fresh arugula ((optional)); 1/2 cup shredded Gruyère cheese