Impossible Shepherd's Pie (Vegetarian)

2 tbsp extra-virgin olive oil

½ cup celery

½ cup carrot

½ cup green peas

½ cup corn kernel

¼ tsp paprika

2 tbsp unsalted butter

½ tsp black peppercorn

¼ tsp garlic powder

¼ cup shredded cheddar

1 parsley

2 tsp salt

1 yellow onion

1 veggie patty

½ cup vegetable broth

1 lb potato

1 pinch garlic

1 tsp worcestershire sauce

½ cup oat milk