In the same wok, leave behind 3 Tbsp of cooking oil and fry the shallots, ginger and garlic until fragrant (10 seconds). Next add the cucumber, tomato and pineapple and cook for a minutes or so. Then you add the sauce mixture, mix well and cover with a lid for a minute. Then add the starch solution and cook until the sauce thickens to your desired consistency. Season with salt if necessary.