Vegetable Curry Samosas

Name: Vegetable Curry Samosas
Ingredients: 2 teaspoons vegetable oil; 1 onion, diced; 1 tablespoon curry powder; 1 tablespoon mustard seeds; 2 teaspoons cumin seeds; 0.5 cup vegetable broth; 2 small potatoes, cut into small cubes; 1 carrot, cut into small cubes; 0.25 pound frozen peas; 1 (17.5 ounce) package frozen puff pastry, thawed; 1 egg, lightly beaten; 2 cups mayonnaise; 0.66666668653488 cup sour cream; 0.5 cup white sugar; 0.5 cup lemon juice; 0.5 cup horseradish; 2 tablespoons curry powder, or more to taste; salt and ground black pepper to taste