You will need:

• 70ml London Dry Gin
• 15ml vermouth
• Green olives 
• 15ml of olive brine (to make it dirty)

To make:

1. Chill a martini glass in the freezer
2. Add gin and vermouth (and brine if you are going for a Dirty Martini) to a mixing glass 
3. Add ice and stir until very cold
4. Strain into the chilled martini glass and garnish with olives or a lemon twist