Prepare your martini glass: If desired, rim the edge of your martini glass by running a lemon wedge around it and dipping it in crushed chocolate cookies or dusting with cocoa powder. Set aside.

Combine ingredients: In a cocktail shaker, add the vodka, chocolate liqueur, heavy cream (or half-and-half), and optional simple syrup.

Add ice and shake: Fill the shaker about two-thirds full with ice cubes. Secure the lid tightly and shake vigorously for about 15-20 seconds. You want the outside of the shaker to feel very cold – this ensures a perfectly chilled and slightly diluted cocktail.

Strain and serve: Strain the mixture from the shaker into your prepared martini glass. Ensure no ice chips make it into the glass.

Garnish and enjoy: Garnish with chocolate shavings or a dusting of cocoa powder. Serve immediately and savor the rich, creamy goodness!