1: Prepare 300 g muffin dough, film it, and put it in the fridge. Note: You can do this the night before with no problem.
2: Peel 3 apples, cut them into wedges, remove the core, then cut them into small pieces, drizzle them with 1 tablespoon lemon juice, and toss to combine.
3: In a small skillet over high heat, melt 30 g butter, and when it becomes frothy, add the apple pieces. Stir, then sprinkle with 30 g caster sugar, and stir again. Cook until the potatoes are tender...
4: ...then transfer them to a bowl and let them cool.
5: Preheat your oven to 180°C (360°F). Once the apples have cooled, mix them into the muffin batter.
6: If possible, pour the mixture into a piping bag—this will make it easier to fill the molds. But you can also use a spoon.