Chill two martini glasses and your cocktail shaker in the freezer for half an hour until really really cold.
Put a few drops of dry vermouth into each glass and swirl it around. Put 3 strawberries into the bottom of each glass – if they’re big ones, cut them into pieces first.
Throw the remaining strawberries and the mint into the cold cocktail shaker and squash them with the end of a rolling pin. Add the ice cubes and the gin or vodka, put the top on and shake it about. Strain into your two martini glasses.