Wash and completely dry strawberries (residual water will prevent the melted chocolate from setting properly). Place a toothpick into the center of the green stem at the top of the strawberry and push the toothpick 3/4 of the way through the berry toward the base.

Place chopped semisweet chocolate in a small microwave-safe bowl with 1/2 tsp. vegetable shortening and microwave for 30 seconds on 30% power. Stir well and repeat until chocolate is completely melted and smooth. (Note: if only a few lumps remain in the melted chocolate, microwave for only 15 seconds on 30% power).

Spoon melted chocolate into an uncut piping bag and seal bag. Place sealed bag in a cup filled with warm water while you melt the white chocolate.

Place the chopped white chocolate and remaining 2 tsp. vegetable shortening in a microwave-safe bowl. Microwave for 30 seconds on 30% power. Stir well and repeat until white chocolate is completely melted, decreasing the last microwave time to 15 seconds if only a few lumps remain in the melted white chocolate.

Remove piping bag of semisweet chocolate from warm water and dry the outside of the bag completely. Cut the tip of the bag near the end so only a small opening is made in the bag.

Working quickly, pick up a strawberry by the toothpick and submerge it almost to the top of the berry in melted white chocolate, swirling to coat well. Lift the berry out of the chocolate and allow excess to drip off. Over the parchment paper, hold the toothpick and berry horizontally with your non-dominant hand. Use your dominant hand to pipe thin stripes of melted semisweet chocolate across the width of the berry, moving down the length of the berry creating 4-5 parallel lines. (Only pipe lines on one side of the strawberry, as the other side will sit on the parchment paper.) Set down the piping bag and pick up a clean toothpick. Gently run the toothpick down the face of the berry perpendicular to the semisweet chocolate lines. The melted chocolate will pull with the toothpick, making the distinct toothed pattern. Do this several times across the berry. Set berry down on parchment paper with the pattern facing up.

Repeat with remaining strawberries, and allow chocolate to harden before serving, about 30 minutes.