A 28 year old woman presents with episodic wheeze, chest tightness and cough, especially at night and with exercise. Spirometry demonstrates an FEV1 of 70% predicted and FEV1/FVC of 0.65 at baseline, improving to FEV1 88% predicted and FEV1/FVC 0.78 after salbutamol. She has symptoms two to three days per week and uses her salbutamol inhaler three times per week. What is the most appropriate controller regimen?