- Place each shortbread cookie in cup of a greased muffin tin. 
- In 2-quart saucepan over medium-low heat, combine butter, sugar and corn syrup. 
- Heat to a full boil, stirring constantly with a wooden spoon. 
- Boil 3 minutes, stirring constantly. 
- Slowly pour in sweetened condensed milk, stirring constantly. 
- Continue cooking over low heat until candy thermometer reaches 220-228 degrees. 
- Remove from heat. 
- Stir in vanilla. 
- Beat until creamy. 
- Immediately stir in toasted coconut and mix well. 
- Spoon mixture by teaspoonfuls over shortbread cookies. 
- Cool completely. 
- Remove cooled cookies from muffin tin onto waxed paper. 
- Melt chocolate chips and drizzle thinly in stripes over cookies and let chocolate harden at room temperature. 
- Store in airtight container.