Heat the oil & butter in a large pan over a medium heat. Add the garlic, mushrooms, tomato & thyme leaves, stirring occasionally until the mixture goes golden and sticky. Add stock to deglaze the pan & bring to the boil, cook for 2 mins, or until liquid has reduced by half. Season to taste & cover to keep warm.
Bring the milk & stock to the boil in a saucepan. Gradually add polenta, stirring constantly. Reduce heat, & continue cooking stirring frequently for 10 minutes or until polenta thickens. Stir in butter & parmesan, then season to taste.
Spoon the polenta onto plates. Add the mushroom and tomato mix on top & drizzle with some of the pan juices. Top with more grated parmesan, sprinkle over some extra thyme & toasted hazelnuts, if using.
(Substitute with creamy, buttery mash if you prefer)