The stir technique is used to prepare a cocktail directly in the glass without ice.
You pour the ingredients directly into the glass and stir gently with the bar spoon before serving.
Check out the bellini recipe.

One more tip

Whenever you prepare a sparkling cocktail (a drink made with sparkling wine and fruit), you must be very careful of the abundant foam that can form due to the reaction of the sparkling wine with the fruit fibre, which can easily come out of the glass and mess up your worktop. To avoid this, first pour in the fruit and then gradually pour in the sparkling wine, stirring gently from time to time to break up the foam that forms.