Cook beans then quickly chill in ice water and set aside. Zest and juice the lemon and set aside, saving the lemon pieces for the stock. In a 2-quart pot, add garlic, lemon pieces, diced kohlrabi and salt to taste and cover with water. Bring to a boil uncovered, then reduce to simmer. Remove the lemon pieces and chunks of garlic to avoid bitterness. Leave uncovered. Check for seasoning and add chopped parsley to assist in flavor of stock.
Add green peas to kohlrabi broth and bring to a quick boil. When peas are cooked (about 3-5 minutes) add fava beans to heat. Drizzle olive oil over stock and let sit covered.
To serve, divide Swiss chard between 6 bowls and add vegetables from the pot, reserving the broth.
Divide broth between each bowl. Top with lemon zest and cheese. Drizzle lemon juice and truffle oil if desired.