Preheat oven to 425°F.

Whisk the flour and salt together in a large bowl. Mix the coconut oil and milk together in another bowl. Add the wet ingredients to the dry ingredients and stir together with a fork until it forms a crumbly mixture. The dough should hold together when you compact it with your hands.

Place equal amounts of the dough into 12 mini tart pans (or 1 large tart pan) sprayed with cooking spray. Using your fingers, press the dough into the pans to line them completely, covering the bottom and up the sides. You can use a glass or flat-bottomed measuring cup to help smooth it out. Prick the crust several times with a fork. Place the pans on a baking sheet and bake in the oven for 10 minutes. Remove the baking sheet from oven. Turn the oven down to 350°F.

While the tart shells are baking, make the filling. Heat the olive oil in a large skillet over medium heat. Add the asparagus, leeks, garlic, thyme and a pinch of salt and pepper. Cook, stirring occasionally, until vegetables start to soften, about 8 minutes. Remove from heat.

Whisk the eggs, milk, ½ teaspoon salt, ¼ teaspoon pepper and cheese together in a bowl.

Place equal amounts of the vegetable mixture in the bottom of each tart shell, making sure to include one or two asparagus tops in the center of each. Pour some of the egg mixture into each tart until it almost reaches the top of the crust. Bake the tarts in the oven at 350°F until set, about 20 minutes (longer if making one large tart). Remove from oven and cool slightly, then remove from the tarts from the pans. Serve.