How to Make It
Grease 2 muffin pans with butter.
Beat the butter and sugar together thoroughly until pale and fluffy, then add the eggs one at a time (don’t add the second egg until the first one has been absorbed completely, to prevent the batter from splitting). Finally, add the flour and the walnuts and mix until well combined.
Cut the plums in half, discard the pits, slice the flesh into large cubes, and mix them into the batter.
Pour the batter evenly into the greased muffin holes and bake in a preheated oven at 400ºF for about 15 minutes or until the muffins are completely golden and crispy on top. Serve warm.