Line two large baking sheets with parchment paper or silicone mats. Preheat your oven to 350°F (175°C).

Spread the pecan halves in a single layer on a baking sheet and toast them for 5 to 7 minutes until fragrant. Allow them to cool completely.

Arrange the cooled pecan halves onto the prepared baking sheets in clusters of three or four nuts, positioned close together to form a small base for the turtle shape. Ensure adequate space between each cluster.

In a heavy-bottomed saucepan, combine the butter, brown sugar, corn syrup, and sweetened condensed milk. Place over medium heat and stir constantly until the butter has melted and the sugar is fully dissolved.

Attach a candy thermometer and bring the mixture to a slow boil. Continue cooking, stirring frequently, until the caramel reaches 245°F (118°C) (firm ball stage). Remove immediately from heat.

Quickly stir in the vanilla extract and salt.

Working quickly while the caramel is hot, spoon a heaping teaspoon of the mixture over the center of each pecan cluster. Allow the clusters to cool and set completely (either at room temperature for several hours or chilled in the refrigerator for 30–45 minutes until firm).

Chop the chocolate, if necessary. Place the chocolate in a microwave-safe bowl and melt in 30-second intervals, stirring after each, until smooth. Stir in the optional shortening or coconut oil if desired.

Carefully lift one set caramel turtle. Dip the bottom of the turtle into the melted chocolate, or place it on a fork and spoon the chocolate over the top, ensuring the caramel is fully encased.

Return the coated turtle to the clean, parchment-lined baking sheet. Repeat for all remaining turtles. Allow the finished turtles to set completely until the chocolate shell is firm and glossy.