Crispy Potato Topped Beef “Pie”

Ingredients

• 2 tbsp olive oil
• 1 brown onion, diced
• 1 celery stalk, diced
• 1 carrot, diced or grated
• 1 zucchini (courgette), diced or grated (grating is good for fussy eaters!)
• 1 tbsp freshly minced garlic
• 1 tsp sea salt flakes
• 2 tbsp thyme leaves or 2 tsp dried thyme, plus extra to garnish
• 750 g minced (ground) beef
• 60 g tomato paste
• 2 tbsp plain (all-purpose) flour
• 1 tbsp red wine vinegar (see note 1)
• 500 ml beef stock
• 1 tbsp Worcestershire sauce
• ¼ tsp freshly cracked black pepper
• 800 g potatoes, very finely sliced (see note 2)
• 3 tbsp melted unsalted butter
• ½ tsp sea salt flakes