Pre-heat the oven to 425°F.Bake the pie crust "blind" by piercing the bottom all over with a fork, placing a piece of tinfoil over it, and filling the foil with beans or another weight. Bake for 15 minutes; remove the foil and weights and return to the oven for 5 minutes so that the bottom browns. Remove and let cool before filling.Note: after using beans for baking blind they cannot be cooked and eaten. Store them in a labelled jar and reuse them indefinitely for this purpose. While the crust is cooking, caramelize the onions in a pan with the olive oil and thyme over medium high heat. Stir often to prevent them from burning, but don't be afraid to cook them until very soft and deep brown.Remove the onions to a bowl when done and crisp up the ham in the same pan. If you ham doesn't have much fat add a little bit more olive oil.Whisk the eggs, milk, cheese, and mustard in a bowl until smooth. Season with salt and pepper.Lower the oven temperature to 375°F.Assemble the quiche by spreading a layer of onions on the bottom, followed by the ham, and finally the egg mixture. Bake for 35-40 minutes, or until the top is golden brown. Note: you can add any leftover Easter vegetables to this quiche as well! Cube them so they're a similar size to the ham and add to the pie shell before the egg mixture. Depending on how much extra you add you may reduce the quantity of egg mixture so that it doesn't spill over the edges.