For the extra ingredients, defrost the frozen spinach and drain very well. Grate the parmesan. Roast pine nuts without fat. Take out and let cool down. Wash basil, shake dry and chop finely.
Preheat the oven (electric cooker: 190 °C). Butter a 12-piece muffin tin. Melt 60 g butter. Beat hot butter, milk and eggs together with a whisk. In a second mixing bowl, mix flour, baking powder, sugar and salt.
Using a rubber spatula or wooden spoon, add the liquid ingredients to the flour mixture and stir only until the two mixtures have just combined.
Carefully fold in ricotta, nuts, spinach and all the herbs. Do not stir excessively! Spread the dough evenly into the muffin tin. Bake in a hot oven for 18 minutes. As a cooking test, prick a muffin with a wooden skewer.
If the skewers stay clean, the muffins are ready. Stick a little more dough on them, put them back in the oven and bake them a few minutes longer. Leave the muffins to rest in their form for 10 minutes, then take them out and let them cool completely on a cake rack.