Preheat the oven to 200°C. Squeeze out excess liquid from the spinach and add it to a pan with 50g butter, olive oil and garlic. Fry gently over medium to low heat for 5 minutes, then remove and season to taste. Stir in feta, olives and lemon juice. Melt the remaining butter and brush onto the sheets of phyllo pastry. Line a large pie dish or individual ovenproof dishes with a few sheets and bake for 5 minutes until golden and crisp. Divide spinach and feta mix accordingly and top with a few more sheets of pastry. Sprinkle with sesame seeds and bake for a further 5 minutes, until golden.