Start by washing, peeling, and chopping all vegetables into even-sized pieces. Uniform cuts ensure even cooking and better texture. I like keeping the pieces slightly chunky for a rustic feel.
Heat olive oil in a large pot over medium heat. Add diced onion and cook until soft and translucent. Stir in garlic and cook briefly until fragrant, being careful not to brown it.
Add carrots and celery to the pot and cook for a few minutes. This helps release their natural sweetness. Stir occasionally so they soften without sticking.
Stir in the diced potatoes and shredded cabbage. These vegetables give the soup its traditional Irish character. Let them cook briefly to absorb the flavors in the pot.
Add diced tomatoes with their juices and pour in the vegetable broth. Drop in the bay leaf and sprinkle in thyme, salt, and pepper. Stir everything together gently.
Bring the soup to a gentle boil, then reduce heat to low. Cover partially and simmer for about 30–35 minutes. The vegetables should be fork-tender and the flavors well blended.
Remove the bay leaf before serving. Taste and adjust seasoning if needed. Stir in freshly chopped parsley for a bright, fresh finish.