Pour oil to a depth of 1 inch in a large deep, heavy-bottomed skillet or pot (preferably cast-iron) or a deep fryer; heat oil to 350°F (175°C). You’ll need about 4 cups of oil.

Toss together oyster mushrooms, 1 tablespoon vegetable oil, lemon juice, and 1/4 teaspoon salt in a medium bowl. Let stand for 15 minutes. Add plant milk; toss to coat.

Meanwhile, whisk together cornmeal, flour, Cajun seasoning, black pepper, and remaining 1/4 teaspoon salt in a shallow dish.

Working in batches, dredge the mushrooms in the cornmeal mixture, shaking off excess. Transfer to a wire rack.

Working in batches, fry the mushrooms until deep golden brown, 3 to 4 minutes. Transfer to a paper towel-lined plate. Sprinkle mushrooms with additional salt if desired.