I would do a higher oven temp, probably 350 degrees F (standard baking temp). However, it might be beneficial to put the tortilla in the muffin tin, add the bean mixture, and start baking that, and get it hot. THEN, pull it out, crack the egg into it, and put it back into the oven for a few minutes to get the egg white cooked and still have the yolk runny.
I've never tried it that way, I may have to experiment.
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