Vegetarian protein

TOFU

This soy-based staple is often pressed into blocks and used in stir-fries.

The clue "Vegetarian protein" points to tofu because it’s a well-known plant-based food made from soybeans, often used as a meat substitute. Tofu is high in protein, making it a staple in vegetarian and vegan diets. The answer is straightforward—no wordplay or hidden meanings, just a direct reference to a common food item.