In a large zipper-seal bag, combine the first eight ingredients. Add mushrooms, shake until well-coated, and refrigerate overnight.
Drain mushrooms into a colander. Place rounded side down on a sheet pan lined with paper towels, and lightly pat dry with another paper towel.
Using a mixer with the whisk attachment, whip the St. Andre®, adding the cream 1 tablespoon at a time and scraping down the sides after each addition.
With a spatula, scrape the whipped cheese into another zipper-seal bag. Seal and snip off the bottom corner of the bag, creating a makeshift pastry bag.
Pipe filling into the mushrooms. sprinkle with lemon zest and serve cold.