1. Preheat the oven to 350°F (180°C). Line a muffin tin with 12 paper liners and set aside.

2. Wash and pit the plums, cut them into small pieces, and mix with the plum jam. Set aside. Melt the butter and let cool down a bit.

3. Mix sugar, melted butter, and vanilla extract in a large bowl. Add the two eggs and two egg yolks to the bowl and mix until light and fluffy (leave the whites in the fridge for the meringue later). In a separate bowl mix flour, hazelnuts, baking powder, and salt. Add together with the milk to the large bowl and mix until just combined. Fold in the plums. Divide the batter between the paper liners. Bake the muffins in the center of the oven for about 18-20 minutes – or until a toothpick inserted into the center of a muffin comes out mostly clean.

4. While the muffins are baking, whisk the two egg whites from the fridge in a clean bowl. Slowly add the sugar and continue whisking until the sugar has dissolved completely, and you got yourself a nice and thick meringue. Fill into a piping bag with a star tip and set aside until needed.

5. Remove the baked muffins from the oven and pipe some meringue on each muffin. Return the muffins to the oven (upper third this time) and bake another 3-4 minutes, so the meringue gets a bit of color. Remove from the oven and let cool completely on a cooling rack. If the meringue is not darkened enough for you, you can use a kitchen torch to touch it up here and there ;) Dust with some ground cinnamon before serving (optional).