Gently fry spring onion in 1/4 cup olive oil for 2-3 minutes. Turn into a bowl and add remaining stuffing ingredients, adding salt and pepper to taste. Remove leaves from cabbage carefully so as not to tear them, counting larger leaves as 2. Par-boil cabbage leaves in boiling water until limp enough to handle, cooking leaves in 2 to 3 lots. Drain in a colander. Cut out larger part of centre rib in each leaf and cut larger leaves in half down centre. Line base of a deep pan with ribs and any torn leaves. Place a generous tablespoon stuffing on base of each leaf, roll up once and tuck in sides to contain filling. Roll to end of leaf. Repeat with remaining ingredients. Crush garlic with salt and blend in crumbled, crushed mint and lemon juice. Pack rolls flap side down in lined pan, sprinkling some of the garlic-lemon mixture and olive oil between layers of rolls. Invert a plate on top of the rolls to keep them intact during cooking. Add enough cold water to just cover rolls and put lid on firmly. Bring to the boil on medium heat, reduce to low and simmer gently for 45 minutes. Remove from heat and leave aside for 30 minutes. Serve lukewarm or cold.