First, clean the mushrooms with a brush to remove debris. Then, slice the stem crosswise into 3 thick rounds, about 2.5-inch tall. Reserve the cap for other dishes.
To make the floret, place one stem in between two chopsticks. The chopstick will be your guide so you don't cut through the stem. Using a sharp knife, criss-cross the mushroom and stop slicing right before you hit the chopstick. Repeat the same step with the remaining stems.
Fill a large skillet with water and set it to high. Once it comes to a boil, season with 1 teaspoon of salt. Carefully drop in the cut stems, uncut side down, into the hot water. Boil while submerging them occasionally until they turn from white to grayish, about 3-5 minutes.
Sieve out and let cool. Then, gently squeeze each stem to remove excess water.
Next, add 1 cup of cornstarch to a large shallow plate, then season with ½ teaspoon of salt and pepper. Mix well. Then, coat the mushroom generously with the starch, rubbing the creases as needed. Transfer to a cleaned plate and repeat with the remaining ingredients.
Now, fill a small saucepan with oil halfway through and heat it to 325F. To check if the oil is ready, drop a small piece of mushroom in, if it sizzles then the oil is ready.
Carefully drop in 1 to 2 mushrooms into the hot oil, the bottom side goes in first, and fry until golden brown. Fry in batches to avoid them from sticking together. Remove and transfer to a paper-lined plate to absorb excess oil.
Mix ½ teaspoon of each in a small bowl until combine: salt, white pepper, black pepper. To put together, heat a large wok with 3 teaspoons of oil and sautè garlic, jalapeños, and scallions until fragrant. Add the mushrooms, salt and peppers then quickly toss to combine. Taste and add more salt if needed.
Drizzle with a splash of toasted sesame oil before serving.