Feed your sourdough starter and let it become leavened and ready to use.
In a large bowl, mix the bread flour, warm filtered water, sourdough starter, salt, and olive oil until no dry flour remains. The dough will look wet and shaggy.
Cover the bowl with plastic wrap or a tea towel and let the dough rest at room temperature for 1 hour.
Complete 3 sets of coil folds, resting the dough for 30 minutes between each set.
Leave the dough on the counter to bulk ferment for 6 to 8 hours.
Before the final rise, divide the dough into pieces weighing about 85 grams each.
Oil each muffin tin, then place one piece of dough into each cup. The dough should only fill each muffin cup about halfway.
Let the dough rise until it looks puffy and fills the muffin tin.
Preheat the oven to 425°F.
In a glass cup, melt the butter, then stir in the Parmesan cheese, red pepper flakes, chopped parsley, pressed garlic, and salt.
Spoon some of the butter mixture over the top of each muffin.
Dimple each muffin the same way you would regular focaccia.
Bake for 18 to 22 minutes.
After baking, brush the muffins with any extra butter mixture.
Remove the muffins from the tin and serve.