Mix butter, oil, water and salt together in a bowl. Add flour a tablespoon at a time, mixing thoroughly. Any lumps will gradually disappear. Preheat oven to 375 degrees. To make filling, combine all ingredients. To make the sambusak, break off walnut sized pieces and roll them into 3 inch diameter circles. Put a teaspoon of filling onto each circle, fold over and crimp edges with finger and thumb. Take care not overfill or the cheese with run out. Lay sambusak on oiled baking sheet and brush with egg yolk and bake for 30 minutes or until golden brown.