Make cheese crisps: Heat oven to 350°F. Grate 2 ounces of Kaltbach Le Gruyère cheese onto parchment paper-lined baking sheet in thin layer. Bake 5-8 minutes or until golden, orange-hued, and lacy. Remove from oven. Cool.
Heat sauté pan over medium heat; add olive oil and onion slices. Sauté about 2 minutes; add garlic, mushrooms and thyme stem. Cook over low for about 5 minutes, stirring occasionally until onions soften. Add sherry and fish sauce and simmer a few minutes. Add stock and simmer over low 20 minutes. Cool, remove thyme stem and strain. Return stock liquid to pan and reduce to 1/2 cup. Salt to taste. Set aside and reserve. Transfer onion and mushroom mixture in strainer to food processor. Add pine nuts. Pulse until minced. Season to taste and reserve. (Alternatively, you can mince the mushroom mixture by hand.)
For the sabayon, combine balsamic vinegar, porcini powder, egg yolks, sugar and splash of sherry in bowl set over simmering water. Add half the reserved stock; whisk mixture, slowly while adding remainder of stock. Whip until thickened and fluffy. Remove from bowl and continue to whip with electric mixer, or by hand, to cool (mixture should still be fluffy). Set aside.
Grill one-third of asparagus stalks over a grill or in cast iron pan. Cut grilled stalks into 1-inch pieces. Cut half the remaining raw asparagus into 1-inch pieces. Blanch them in boiling water for 30 seconds; drain and plunge them immediately into ice water bath to cool. Drain. Cut remaining asparagus into thin slices. Toss all asparagus in a bowl along with juice from the 1/2 lemon, salt and black pepper.
Spoon small pool of reserved sabayon on four plates. Place mushroom mixture and asparagus pieces on plates, dividing evenly. Shave remaining Le Gruyère cheese over each salad. Divide Le Gruyère cheese crisps over salads.