Preheat the oven to 230C / 210 fan.
Bring a large pan of salted water to the boil. Add the potatoes and cook for 10 - 15 minutes on a medium / low heat until just tender to insert a knife. Drain, rinse and allow to cool slightly.
Add the potatoes to a non stick baking tray and toss with 2.5 tbsp olive oil, salt, pepper, 1 tbsp fresh thyme leave and 1 tbsp fresh rosemary. Toss to combine, crush the potatoes slightly with the bottom of a glass and roast for 25 - 30 minutes, turning once, until crisp on the outside and fluffy in the middle.
Meanwhile, heat the remaining 2 tbsp of olive oil in a pan. Add the onions, carrot and celery and fry on a medium heat for 4 minutes. Add the garlic + 1 tbsp fresh thyme for 1 minute until fragrant.
Add the stock and miso and bring to the boil. Reduce the heat and simmer for about 20 minutes until thicker. Add the beans, peas and sweetcorn, salt and pepper and warm through for about 3 minutes.
Remove 1.5 cups of soup and place in a jug. Puree with a hand blender and then add back to the soup. This will make it super tasty and thicker without needing to add any cream or starchy thickeners.
Stir through nutritional yeast and apple cider vinegar. Adjust seasoning to taste and top with fresh thyme, crispy smashed potatoes (don't forget the crisped up herbs in the tray... best bit) and an optional drizzle of olive oil.