Remove any damaged outer leaves from the cabbage: Finely chop enough cabbage to measure 4 cups (280 g), cutting the pieces into approximately ¼-inch (6 mm) squares. Transfer the chopped cabbage to a large mixing bowl. This should take about 4 minutes, and the pieces should be small and evenly sized.

Wash the English cucumber and trim both ends: Dice it into approximately ¼-inch (6 mm) pieces, leaving the thin skin on for extra color and crunch. Add the cucumber to the bowl with the cabbage. This should take about 3 minutes.

Thinly slice the scallions and roughly chop the baby spinach. Add both to the large mixing bowl. Gently toss the vegetables for about 30 seconds until evenly distributed. The mixture should look colorful, with plenty of light and dark green pieces.

Cut the avocado in half, remove the pit, and scoop the flesh into the blender. Add the Greek yogurt, basil leaves, parsley leaves, lemon juice, olive oil, chopped garlic, Dijon mustard, salt, black pepper, and cold water. This should take about 3 minutes. Make sure the avocado flesh is soft and free of any dark or damaged spots.

Secure the blender lid and blend on medium-high speed for 45 to 60 seconds, stopping once to scrape down the sides with a spatula if needed. The dressing should become smooth, creamy, and bright green, with no large pieces of herbs or avocado remaining. If using a food processor, process for approximately 1 to 2 minutes until well combined.

Pour the green goddess dressing over the chopped vegetables. Use a large spoon or spatula to fold everything together gently for 1 to 2 minutes. Continue mixing until the vegetables are evenly coated and there are no large pockets of dressing at the bottom of the bowl.

Let the dressed salad stand at room temperature for about 1 minute, then gently toss it again for 20 to 30 seconds. The cabbage should still feel crisp, the cucumber should remain firm, and the dressing should cling to the vegetables without pooling excessively.

Divide the salad evenly among six serving bowls or transfer it to one large serving bowl. Serve immediately while the vegetables are cold and crisp. The finished salad should have a creamy coating, fresh green color, and a crunchy texture.