Roast Knuckle with Veggies

Name: Roast Knuckle with Veggies
Ingredients: 1 tablespoon vegetable oil; 2 onions (roughly diced); 2 carrots (roughly diced); 1.333 cups Celeriac (roughly diced); 1 clove garlic; ½ teaspoon ground Caraway seed; 4 small Pork knuckles; ⅞ cup dark beer; 1.333 cups Meat stock; gravy thickener (as needed); 2 tablespoons butter; 2 carrots (cut into decorative shapes); 2 Parsnips (cut into decorative shapes); 1 tablespoon olive oil; 2 large Red onions (sliced into rings)