Ingredients:
· 2 small Yukon gold potatoes, very thinly sliced
· ½ medium red onion, thinly sliced
· 1 cup asparagus, cut diagonally into 1-in. pieces
· 1tbsp olive oil
· Salt and pepper to taste
· 1 cup cheese, coarsely grated
· 1 refrigerated rolled pie crust
· 1tbsp Dijon mustard
· 1 large egg
· Mixed green salad, optional

Method:
Heat oven to 200°C. In a large bowl, toss together the potatoes, onion, asparagus, olive oil and one-fourth teaspoon each of salt and pepper. Add the cheese and toss to combine. Working on a piece of parchment paper, roll the pie crust into a 12-inch circle. Slide the paper and crust onto a baking sheet. Spread the mustard on the pie crust, leaving a three-inch border around the edge.
Spoon the potato-asparagus mixture onto the pie crust, leaving a two-and-a-half-inch border around the edge. Fold the border over the mixture. In a small bowl, whisk together the egg and a tablespoon of water. Brush the crust with the egg mixture and bake until the crust is golden brown and the vegetables are tender, for 30-35 minutes (cover with foil if the crust is browning too quickly). Transfer to a cutting board and cut into pieces. Serve with a salad, if desired.