Soak the cashews in a bowl of water overnight (or for at least 4 hours). Drain and rinse well.
In a high speed blender, blitz the drained cashews, water, oil, lemon juice, mustard, garlic and capers until smooth and creamy. If necessary, add a little more water, sparingly, to make it a thick drizzling consistency. Season with the salt and pepper.
For the herby croutons
Tear the bread into bite-sized pieces, then toss in a bowl with the olive oil and herbs to coat.
Heat a frying pan over a medium heat and pan fry the bread pieces until crispy.
Heat a grill pan until hot.
Meanwhile, slice the little gem lettuces into quarters lengthways. Drizzle with the olive oil and use your hands to coat it thoroughly.
Place the lettuce quarters onto the hot grill pan and sear to create char lines.
Divide the lettuces onto plates, drizzle with the dressing and top with the croutons. Sprinkle with the nutritional yeast and enjoy immediately.