In a second bowl, stir together the butter, salt and sugar until frothy. Gradually add the eggs and whisk well with the butter mixture. Fold in the flour mixture and carefully add the oat flakes, muesli, apple pieces and chopped nuts.
Using a teaspoon, prick small heaps out of the dough and place on a baking sheet lined with baking paper.
Bake in a preheated oven at 180 ° C for about 15 minutes. When the biscuits are ready, place them on a wire rack and let cool down well.
Tip: If you like, you can replace the pecans with walnuts.