Cut chicken into strips. Place chicken and garlic in a bowl. Stir to combine. Chill, covered, 1 hour. Cut or tear oak leaf lettuce, curly endive and radicchio into small pieces. Place in a large bowl.
Heat butter in a nonstick pan over medium heat. Cook chicken until golden brown and cooked through, about 5 minutes. Add salt and pepper to taste.
To make dressing, whisk sour cream, yoghurt, oil, vinegar and mustard in a bowl until combined. Add salt and pepper to taste. Stir dressing into salad greens. Distribute salad greens among serving plates.
Peel thin strips of rind from lemon. Place chicken, spring onions, mushrooms and lemon rind on top of salad greens.