Place the butter and sugar in a bowl and beat with an electric mixer until pale and fluffy. Add the eggs one at a time, mixing with each addition.

In a separate bowl, mix together 1 ½ cups of flour, baking soda and salt. Add this to the butter mixture in 2 additions, alternating with sour cream. Mix the peaches with 1 tbsp flour and add to the batter, along with the vanilla extract and ¾ tbsp peach jam.

Pour the batter into a buttered and floured doughnut pan and tap several times to remove any air bubbles. Bake the doughnuts at 350F for 15-20 minutes. Let the doughnuts cool in the pan for 15 minutes, then remove them from the pan and transfer to a cooling rack and fully cool.

Combine ¼ cup peach jam with ¼ cup water. In a separate bowl, combine the sugar and cinnamon. Working with one doughnut at a time, brush each doughnut with the peach jam glaze. Dunk the doughnuts into the cinnamon and sugar. Skewer mini marshmallows onto toothpicks and brush with the jam glaze. Coat the marshmallows in cinnamon sugar and stick them into the doughnuts to create sandcastles. Stick some washi tape onto a toothpick and stick it into the top of each sandcastle to look like a flag.

Divide the melted white chocolate into two bowls and dye them coral and light purple with the oil-based food colouring. Spoon the chocolate onto a tray lined with parchment paper and shape them into starfish. Place the tray in the freezer for 5-10 minutes until the chocolate is fully set.

To serve, sprinkle some brown sugar onto a tray to look like sand, and place the doughnuts on top. Top with the chocolate starfish and enjoy!