Question: I wanted to bake a milky bread loaf though was told that I couldn’t. Is that true and why?
Answer: The Gemara (Pesachim 30a; 36a) writes that chazal instituted that one mustn’t bake a loaf of bread using milky or meaty ingredients as people may not realize and come to eat milky bread in a meaty meal, or vice versa (See Shulchan Aruch YD 97:1).
The Aruch Hashulchan (YD 97:1) writes that this is so serious that if one accidentally baked such bread, one mustn’t eat it at all (See Kaf Hachaim YD 97:11; Yabia Omer YD 1:5).
The Gemara writes that one may bake milky or meaty bread, however, providing that they bake it kaein tura, like the eye of an ox. According to Rashi (Pesachim 36a) this refers to baking a small quantity while Rambam (Maachalos Asuros 9:22) understands it to mean baking the bread in a different shape to regular bread.
The Shulchan Aruch (ibid) writes that if either of these conditions were met, one could bake such bread. Thus, in Yerushalayim, all milky borekas are made in a triangular shape. While the Shulchan Aruch limits this small amount to the amount that one eats in one meal, the Rema says it equals the amount of bread that one will eat in one day.In conclusion, you may bake milky bread providing that you either bake a small quantity, or shape it differently to usual.