Make a simple syrup by dissolving a 1/2 cup of sugar in the water in a small saucepan. Bring to a boil and remove from heat to cool.
Combine the strawberries, ice cream, milk and vodka in a blender, and blend on high speed until smooth.
Chop the shortcake into breadcrumb-sized pieces. Toast in an even layer on a parchment lined baking sheet in a toaster oven or in a standard oven at 200º F for 3-4 minutes until golden and slightly dry.
Meanwhile, beat the whipping cream until it begins to thicken. Add the teaspoon of sugar, and then continue beating just until stiff peaks form.
Add a shortcake rim to your glasses by dipping the glasses into a 1/4 inch of simple syrup and immediately rolling the rims in the shortcake crumbles.
Fill the glasses with the strawberry milkshake and top with a generous dollop of whipped cream. Garnish with a strawberry slice.