Winter Root Vegetable Soup

Name: Winter Root Vegetable Soup
Ingredients: 2 medium carrots; 2 medium parsnips; 2 medium potatoes; 2 medium sweet potatoes; 1½ medium red onions (or 2 small); celery root/celeriac piece (the size of a medium potato); 2-3 garlic cloves (unpeeled); 1 teaspoon dried herbs (such as herbes de Provence); 1 teaspoon paprika; 2 tablespoons olive oil; 1 tablespoon butter (any); 4½ cups vegetable stock (hot); ½ teaspoon fine sea salt (and pepper to taste - rainbow coloured peppercorns work well)