Locked chocolate squares restrict the board. However, only locked chocolate squares on fourth row can spread because locked chocolate squares on sixth and eighth row are blocked by conveyor belt, so they will not spread.
The orders are worth 15,000 points.[1] Hence, an additional 15,000 points is required to earn one star.
Stars[]
Stars
Score
2,100
38,125
73,000
146,000
Strategy[]
The locked chocolate is merely a temporary impediment - once you fire off a couple of special candies, the order resolves very quickly with limited need for thought and certainly no need to worry about spreading chocolate.