Preheat the oven to 350 degrees Fahrenheit and grease the skillet with melted butter.
In a saucepan, add the buttermilk and milk and let them simmer until they are warm and not boiling.
After they start simmering, add in the cornmeal, bit by bit, while whisking constantly.
Reduce the heat to a minimum and let the mixture cook until it is thick while stirring occasionally.
After 10 minutes, your mixture should be ready, and you can take it off the heat.
Add three tablespoons of butter, thyme, salt, and black pepper, and whisk the mixture until the butter melts and everything is combined. Let it sit for 10 minutes.
In a large bowl, crack the eggs and separate the yolks from the whites, ensuring that there isn’t a single drop of yolk in the egg whites.
Add the cornmeal mixture to the egg yolks and whisk once it has cooled down. Transfer the mixture to the saucepan and heat over a very low flame for a minute or two until everything is combined.
Whisk the egg whites using an electric mixer until it forms stiff peaks.
Afterwards, start folding the egg whites into the egg yolk and cornmeal mixture, bit by bit and gently, in a large bowl.
Once everything is mixed together, transfer the batter into the greased cast iron skillet and bake for 35-40 minutes.
After the 40-minute mark, take the bread out of the oven and let it cool down for 5-10 minutes, after which you can serve it hot or warm.