How to make
Beat the eggs with the sugar. Add the oil, flour with baking powder and vanilla to them. Stir well.
After that, add the walnuts and plums. Distribute the mixture into a muffin tin with paper muffin cups in each.
Put the flour, cold butter and sugar in the food processor.
Grind the ingredients, so that they turn into crumbs.
Sprinkle the topping over the muffins. Bake them at 360°F (180°C) for about 20 minutes.
The muffins with plums and crunchy topping are ready.