Make the Dark Cherry Syrup: Simmer cherries, sugar, and lemon juice until thickened. Strain for a smooth sauce. Chill.
Make the Black Cocoa Drizzle: Mix chocolate syrup with black cocoa powder until smooth. Chill.
Prepare the Blue Vanilla Cream Base: Blend milk, vanilla ice cream, vanilla syrup, sugar, and optional blue food coloring with ice until smooth.
Assemble the Drink: Layer blue vanilla cream in the cup, swirling in dark cherry syrup and black cocoa drizzle for a blue-red-black marble effect.
Top & Finish: Add whipped cream, drizzle with cherry syrup, and sprinkle with blue sugar crystals.
Serve immediately for the freshest flavor and most dramatic gothic night presentation.