Curried Vegetable Pot Pie

Name: Curried Vegetable Pot Pie
Ingredients: 1 small onion, quartered; 1 2-inch piece of ginger, peeled; 2 cloves garlic; 1/2 to 1 serrano pepper, stemmed; 3 tablespoons unsalted butter; 1 10-ounce box frozen chopped spinach, thawed and squeezed dry; 1 pound Yukon Gold potatoes, cut into ¾-inch pieces; 1 15-ounce can chickpeas, liquid drained and reserved; 2 teaspoons madras curry powder; Kosher salt and freshly ground pepper; 1/3 cup heavy cream; 1 sheet frozen puff pastry, thawed; Chutney and plain yogurt, for serving