Pre-heat the oven to 400 degrees and transfer the puff pastry from the freezer to the counter and let thaw for 20 minutes until you can unfold it without breaking it.
Prepare Puff Pastry: Spray the tart tin with cooking spray. This next step will vary, depending on the size of your tart tin. Since mine is thin and long, I cut the puff pastry in half length wise, dabbed some water on two ends and attached them by rolling them with a rolling pin (see photos or video in post). Sprinkle a tiny bit of flour on a baking surface and roll the puff pastry out until it is about 1/2 an inch wider than the tin on both sides, then transfer it to the tin. Press down the sides and discarded the extra pastry. Place it in the refrigerator to chill.
Boil Vegetables: Now bring a large stock pot filled with water to a boil. Cut the asparagus in half length wise, and chop off the rainbow chard leaves, trying to keep as much of the middle stem as possible. Once the water is at a roaring boil, toss in the asparagus and rainbow chard stems and boil until soft enough to manipulate, about 5-7 minutes. When done, drain and transfer to a bowl filled with ice water for 2 minutes before beginning to weave.
Lattice Vegetables: Weave the asparagus and rainbow chard in an alternating pattern (asparagus, chard, asparagus, chard). Start by lining up the 'columns'. The rainbow chard pieces should cover the entire length of the tart tin, however the asparagus will not. Overlap another piece of asparagus over the end of the first asparagus to make one long asparagus. Now weave the shorter asparagus and rainbow chard in 'rows', trying to keep them as close as possible until you reach the end. (see photos & video in post)
Make Filling: Now make the tart filling. Pour your egg whites into a bowl, and toss in the garlic powder, chopped onion and crumbled goat cheese. Season with a pinch of salt & pepper. Stir well to combine. Remove the tart from the fridge, and pour the egg mixture into the tart (it's okay if you spill some).
Transfer Woven Topper: Using two spatulas, carefully transfer the woven asparagus and rainbow chard to the top of the tart. This step was actually very easy, as long as they were woven tight enough. Position accordingly, then using kitchen scissors, chop off the excess vegetables so they fit perfectly in the tin.
Bake: Place the tart tin on a baking sheet and put it in the middle of the oven. Bake until the sides begin to turn golden brown, about 40-45 minutes. Remove and let sit for 10 minutes before cutting. Garnish however you like, and enjoy!