Preheat oven to 375°.
Line a large 10x15-rimmed baking sheet with parchment paper, secure the parchment on the corners with stainless steel oven-proof clips, and layout 126 square pretzel snaps in a single layer.
Sprinkled 2 cups of toasted pecan pieces on top of the pretzels and set aside
In a small heavy saucepan, combine the unsalted butter, light brown sugar, and vanilla extract and heat over medium-low heat, stirring constantly until melted. Once melted, use a whisk to ensure everything is well incorporated. Once the mixture begins to boil, stir constantly for three minutes.
Carefully pour the praline caramel over the pecans and pretzels, distributing it as evenly as possible, then transfer the pan to a 375° oven for 10 minutes.
After ten minutes in the oven, carefully remove the pan to a wire rack.
Place four ounces of Ghirardelli Milk Chocolate Melting wafers in a piping bag and set it in a microwave-proof glass, microwave for 30-second intervals until it is completely melted. Snip the tip of the bag and pipe the chocolate horizontally across the pecan praline pretzels.
Repeat the melting process for the four ounces of Ghirardelli White Chocolate Melting wafers, snip the tip of the bag, and pipe the white chocolate vertically (in a different direction) across the milk chocolate.
Repeat the melting process again for the four ounces of Ghirardelli Dark Chocolate Melting wafers, snip the tip of the bag, and pipe the dark chocolate diagonally (in another direction) across the white chocolate.
Allow to cool to room temperature, then refrigerate for about an hour or until chocolate is hard. Then, remove the parchment from the pan and break it back into individual pretzel squares.