Line a muffin tin with 12 paper liners. Preheat the oven to 180C.
To brown the butter; heat the butter in a saucepan or small frying pan over medium heat and whisk continuously until the butter begins to foam and darkens and smells nutty. Be very careful not to burn it! It changes very quickly - so it is worth only focusing on this one thing whilst doing it. Set aside and allow cool for a few minutes in a bowl.
120 g butter
In a medium mixing bowl, whisk together the plain flour, rolled oats, brown sugar, baking powder spices and sea salt.
210 g plain flour, 100 g old fashioned rolled oats, 2 teaspoons baking powder, 1 ½ teaspoons ground cinnamon, ¾ teaspoon ground ginger, ¾ teaspoon ground allspice, ¼ teaspoon ground nutmeg, ¼ teaspoon ground cardamom, 100 g soft brown sugar, ½ teaspoon fine sea salt
In a large mixing bowl, whisk together the eggs, milk and apple sauce until smooth and well combined. Mix in the brown butter from step 2 and vanilla extract.
2 medium eggs, 180 ml milk, 125 g apple sauce, 1 teaspoon vanilla extract
Add the dry ingredients to the wet ingredients.
Stir with a wooden spoon until just combined- some streaks of flour are good.
Add the chopped apple to the bowl - and gently stir in. Do not overwork.
1 medium apple
Divide the mixture between the liners in the muffin tin. Top the batter with the apple and old fashioned oats if using.
2 tablespoons old fashioned rolled oats, sliced apple, 2 tablespoons chopped hazelnuts
Bake for 20-25 minutes until risen and golden and a cake tester comes out almost clean. Leave to cool in muffin tin for 5-10 minutes and then transfer to a wire rack to cool completely. Drizzle the muffins with brown butter caramel and enjoy!