Stir together 1/3 cup creamy peanut butter, 1/3 cup Biscoff cookie butter, 1/4 cup powdered sugar, 2 tablespoons finely crushed Biscoff cookies, 1/2 teaspoon vanilla extract, and 1 pinch salt until a soft truffle dough forms. Chill the full mixture for 10 minutes.

Divide the chilled filling into 8 equal pieces, then roll each piece into a small ball that fits comfortably inside one ghost cavity.

Microwave 10 ounces chopped white chocolate at 50% power in 30-second intervals, stirring after each interval until smooth. Stir in 1 teaspoon refined coconut oil only if the coating needs thinning.

Divide about half of the melted 10-ounce white chocolate batch among 8 ghost cavities. Use the back of a small spoon or a food-safe brush to coat the bottoms, sides, and rims, then chill for 5 minutes.

Place 1 of the 8 truffle balls inside each chilled shell. Cover all 8 cavities with the remaining white chocolate from the 10-ounce batch, spread it to the rims, and tap the mold gently to remove air pockets.

Refrigerate the filled mold for 20 to 30 minutes, until all 8 ghosts feel firm. Peel the silicone away from each truffle, then trim thin chocolate edges with a small sharp knife if needed.

Finish all 8 truffles with black writing icing, melted dark chocolate, an edible marker, or candy eyes as desired. Let any added decoration set before serving.