Soak 150ml hot water with 4 tsp Oolong tea leaves for 20 minutes, drain well. Warm up Oolong tea in microwave at high heat for 1 minute. Add dried longan pieces into Oolong tea and soak for 30 minutes.
Cream butter and sugar until pale. Add eggs, one at a time, beating well between each addition.
Sift flour, baking powder and salt over. Mix well at low speed.
Add dried longan and tea. Fold well with a rubber spatula.
Spoon mixture into desire (greased) moulds at ¾ full. Bake at preheated oven for 20 minutes or until golden brown.
Cool cakes slightly, then turn out onto wire rack to cool completely.
Recipe by Anncoo Journal at https://www.anncoojournal.com/longan-oolong-cake/