1. For the Yorkshire pudding,whisk the flour,eggs,milk and salt together to form a smooth batter and rest in the fridge overnight* in an airtight container (see tip). Remove from the fridge one hour before cooking to come to room temperature.
2. Heat your oven to 200C (180C fan-forced). In an ovenproof frying pan,melt the butter. Dip the portobello mushrooms cap down into the butter before removing from the pan. Add the sliced mushrooms,onion and garlic and stir to combine. Place the portobello mushrooms on top and scatter with salt,pepper and thyme sprigs. Roast for 15 minutes until the portobellos are tender.
3. Increase the oven to 230C (210C fan-forced). Heat an ovenproof frying pan around 26cm diameter over high heat until very hot,then add the oil. Pour the pudding batter into the pan and immediately place into the oven for about 20 minutes,until the pudding is puffed and cooked through.
4. Meanwhile,remove the portobellos from the pan and place the frying pan over high heat. Stir the Swiss brown mushrooms and add the wine,cream and mustard and bring to a simmer for a minute or two so it reaches a sauce consistency,then add the vinegar and keep warm until ready to serve.
5. When the pudding is ready,remove it to a plate. Place the portobello mushrooms inside and pour over the sauce. Add the peas,scatter with parsley and serve.
*Tip:When making Yorkshire pudding batter,an overnight rest relaxes the gluten for greater rise. But bring the batter to room temperature before cooking or you won't get maximum puff.
Find more of Adam Liaw's recipes in theGood Food Favourite Recipes cookbook.
Correction:An earlier version of this recipe listed the butter quantity as 450g. This has since been updated.