- Preheat oven to 375 degrees.
- Toss Jerusalem artichokes with olive oil, salt, and black pepper. Roast until just tender, about 15 to 20 minutes.
- While artichokes are roasting, heat a couple of tablespoons of olive oil in a pan over medium-high heat. Sear onions on their cut sides until nicely caramelized and tender.
- If using fresh English peas you will need to blanch them in salted boiling water until they are tender, about 5 minutes. If you are using frozen peas you can add them into the sauté as you finish.
- Season swordfish on both sides with salt and black pepper. Heat a pan over medium-high heat and add just enough oil to coat. Sear swordfish on the first side until golden brown. Flip the steaks over and reduce heat to low.
- Add 4 tablespoons of butter, thyme, and a splash of white wine vinegar. Baste fish with the butter vinegar mix until it is cooked to a medium temperature. Remove swordfish from the pan onto paper towels and allow to rest.
- Combine onions, peas, and artichokes in a pan and heat through over medium heat. Add remaining butter, a splash of white wine vinegar, and season to taste with salt and black pepper.
- To plate, divide vegetables evenly on each plate and serve fish on top.