Simmer the oat groats in plenty of water for 30 minutes
Strain the groats under cold water and set aside
In a bowl, combine the boiled oat groats, the white bread flour, fine oatmeal, the yeast and salt, the grated apple and the tepid water
Form a dough and knead for 10 mins
Place the dough back in bowl for 1 hour or so for its first rise
Punch down the dough, then shape into a round loaf and place into a pre-floured round bread banneton
Proof for several hours at room temperature until fully risen (the time this takes will depend on the temperature in your room)
Preheat the oven to 220°C (if you are using a La Cloche baking dome, preheat the dome in the oven from cold)
Bake at 220°C for 1o minutes, then at 200°C for another 50 minutes
Cool on a wire rack