Spread pecans out onto a baking sheet and bake for 5-10 minutes, stirring once, until toasted and fragrant (but not burned!). (Alternately, you can heat them in a hot skillet stirring constantly until they are fragrant, about 5 minutes.)
Once cooled, roughly chop the pecans and set aside.
Prepare a baking sheet with parchment paper or a silpat liner. Set aside.
Place butter in a large microwave safe bowl and heat in microwave until melted.
Add brown sugar, granulated sugar, sweetened condensed milk, and corn syrup and stir well to combine. Fill a small cup with ice and water and set aside.
Return bowl to microwave and cook mixture on HIGH power for 6 minutes*.
Use hot pads to carefully remove the bowl from the microwave. Spoon a small spoonful of the caramel into the bowl of ice water. Use your fingers to pinch the caramel—it should form into a pliable ball (not too soft, but pliable and not hard.) If it wont come together to form a ball in your fingers, return it to the microwave for an additional 30 seconds, and test again..
Stir vanilla into hot caramel. Stir in chopped pecans.
Drop spoonfuls of the mixture onto the parchment paper lined baking sheet to create individual mounds of caramel candy. (I usually get about 20, but you can make the candies as small or large as you like). Refrigerate until set, about 20 minutes.
Reserve a handful of chopped chocolate off to the side and melt the rest in a double boiler (I just place a large heat-proof bowl over a pot of simmering water), or in the microwave in a heat proof bowl, stirring every 20 seconds until melted and smooth. Remove from heat and stir in the remaining chopped chocolate that you set aside (this will temper the chocolate to help it set up better).
Use a large skewer or a spoon to dip caramel clusters in chocolate and gently remove them to the parchment paper. Allow to set up in the fridge.
Store turtles in an airtight container at room temperature, (or in the fridge if you live in a more humid climate) for up to 2-3 weeks. Allow to come to room temperature before serving.
Microwave Caramel: My caramel takes about 6 minutes in the microwave, but time may vary depending on the wattage of your microwave.Use the ice water method or a candy thermometer to test if the caramel is ready. I’ve found the ice water method to be more reliable, but if using a candy thermometer it should register between 238 - 240 degrees.Chocolate: Make sure you’re using high quality chocolate! I prefer Baker’s or Ghirardelli brands.