Combine oil, lemon juice, caster sugar, thyme leaves and salt and pepper in a large bowl and whisk until well combined.
Set aside 2 tblsp dressing to add later.
Add mushrooms to the large bowl and stir gently to combine, then cover and set aside for 30 minutes.
Meanwhile cook beans in a saucepan of salted boiling water for 2 minutes, until bright green.
Drain and refresh in cold water, allow to drain & come to room temp, and cut into thirds.
Preheat barbecue plate on high.
Cook the mushrooms, turning occasionally for 3-4 minutes until golden. Remove from bbq plate and set aside to cool to room temperature.
Meanwhile, combine beans, tomatoes, spinach (or rocket) and parmesan in a large bowl.
Add the reserved dressing, mushrooms, salt and pepper and toss to combine.