My last experiment worked out quite well. No separation of the batter, and the texture of the final waffle way quite nice. The only issue was that the batter became relatively thick. The result was a smaller waffle, since much of the batter stuck inside the beaker I was growing it in. This new recipe compensates for that.

Ingredients:
56.4g unbleached white all purpose flour
43.2g ripe sourdough starter
54.6g whole milk (room temperature)
36.6g mineral water (room temperature)
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30g egg (warmed in a water bath) and then lightly beaten
1.5g fine salt
4.8g fine sugar
33.6g melted European style butter (at 43ºC/110ºF)

Directions:

1. In a medium bowl, combine the flour, sourdough starter, and milk. Stir lightly to blend.
2. Add the water to the mixture. Stir to completely blend, and then cover the bowl with plastic wrap. Let it rest 3 hours at room temperature.
4. Then add the egg, salt, sugar and butter. Mix to blend completely, but do not overmix.
5. Transfer the batter to a 500ml or 2 cup measuring cup with volume markings. The batter should be ~215ml in volume.
6. Allow the batter to rise for 3 hours (little activity will have occurred), stir, and then give an overnight rise of 9-10 hours, until it reaches 385ml in volume.
7. Pour your batter into a preheated iron at 188ºC/370ºF, and cook for 3 minutes 35 seconds.

Allow the cooked waffle to cool until it reaches 49ºC/120ºF, and then place it back on the iron to cook for 10 seconds.