Preheat the oven to 400F. Melt the butter (1 tablespoon) in a 10-inch non-stick or stainless steel skillet over medium heat. Once the butter is hot and frothy, add the sliced leek (1 small, trimmed and sliced) and pinch of salt (~1/4 teaspoon). Cook for 6-7 minutes, stirring occasionally.

Add the chopped asparagus (1 small bunch) to the pan, along with another pinch of salt (~1/4 teaspoon). Let the veggies cook for another 2-3 minutes, stirring occasionally, until the asparagus is bright green, and the leeks are soft and starting to brown on the edges. Remove the pan from the heat and stir in the frozen peas (1/3 cup). Let the veggies sit in the pan to cool and let some of the moisture evaporate while you mix up the custard.

In a large measuring cup or small bowl with pour spout, whisk together the eggs (3 large), egg yolks (2), heavy cream (1/2 cup), milk (1/4 cup), chives (2 tablespoons), lemon zest (optional – from 1/2 lemon), fresh ground black pepper (1/4 teaspoon), and salt (1/2 teaspoon). The mixture should be thick and smooth.

Prepare the wells of a 12-hole silicone muffin pan with cooking spray and then set the silicone pan on a flat baking sheet (so it’s easy to move). Divide the cooked vegetables between each well, then fill each just over 3/4 full with the custard mixture. Do your best to divide the custard mixture evenly. Scatter the shredded cheese (1/2 cup) over the tops of the quiches, and then a tiny pinch of salt and pepper on each.

Bake the quiches in the preheated oven for 18-20 minutes total, rotating the pan after the first 10 minutes to promote even cooking. The quiches are done when the cheese on top is browned and a knife or toothpick comes out clean. Cool in the pan for about 5 minutes before transferring them to a wire rack.

Serve quiches warm or at room temperature. Store leftovers in an airtight container in the fridge for up to 3 days for best quality. Reheat quiches on the stovetop (in a nonstick pan on low until steaming; slice horizontally or dice for quicker heating) or in the air fryer (300F for 6-7 minutes).