Place the freeze-dried raspberries in a food processor. Pulse until finely ground into a powder. Using a fine-mesh sieve, sift the powder to remove any seeds or larger particles. Set aside the sifted powder for later use.

In a large, heatproof bowl, combine the chopped white chocolate and the cubed butter. In a small saucepan, gently warm the heavy cream over medium heat until it just begins to simmer. Remove the cream from the heat and pour it directly over the white chocolate and butter. Allow the mixture to sit undisturbed for 3 to 5 minutes.

After resting, stir the mixture gently with a spatula or whisk until the chocolate and butter are fully melted and the mixture is smooth and cohesive.

Add half of the sifted raspberry powder to the ganache and stir to combine. Taste the mixture, and if a more pronounced raspberry flavor is desired, add additional powder to preference.

Cover the surface of the ganache with plastic wrap, pressing it directly onto the surface to prevent a skin from forming. Refrigerate for a minimum of 2 hours, or until the ganache is firm and scoopable.

Line a baking sheet with parchment paper. Using a mini cookie scoop or small spoon, portion the chilled ganache into 1-inch mounds. Roll each portion between your hands to form smooth, round balls. Place the truffles onto the prepared baking sheet.

Transfer the truffles to the freezer for approximately 30 minutes, allowing them to firm up before dipping.

Melt the semi-sweet chocolate using a double boiler or in a microwave-safe bowl, heating in 20-second intervals until smooth. Dip each frozen truffle into the melted chocolate, using a fork or dipping tool. Gently tap off excess chocolate and return the coated truffle to the parchment-lined tray.

While the chocolate is still wet, immediately sprinkle the truffles with your choice of toppings. Work in small batches to ensure the toppings adhere before the coating sets.

Refrigerate the finished truffles for approximately 15 minutes, or until the chocolate shell is completely set. Serve chilled or at room temperature.