Place kernels in a small pot, add just enough water to barely cover, and bring to a boil. Reduce to simmer until the water is nearly gone.
Fill a medium pot halfway with water, place the steamer basket on top, and bring to a gentle simmer.
Fold a piece of parchment paper in half like a book and crease firmly.
Open and place 2 slices of butter near the crease, then lay seasoned salmon on top.
Add shallots, spinach, and one more slice of butter over the salmon.
Fold into a sealed half-moon packet using small overlapping pleats around the edge.
Place the packet in the steamer basket. Cover and steam on medium-low heat for 10 minutes.
Blend the cooked corn with cream cheese and a small pat of butter until smooth.
Pass through a sieve for extra silkiness. Stir in chopped parsley.
Heat a skillet over medium-high heat. Add a high-heat cooking fat (e.g., avocado oil).
Sear zucchini pieces on all sides until golden and tender. Remove from heat.
Spoon corn purée in the center of the plate. Lean zucchini around the edge.
Carefully remove salmon from parchment and place just off-center on the purée.
Drizzle any buttery juices from the papillote over the top. Finish with truffle salt if desired.