The Shabbath meals require Lehem Mishneh (two loaves of bread) to be brought to the table . This is because of the double portions of manna that fell on Fridays in the desert because of Shabbath. (As mentioned previously, according to Rabbenu the Ari z"l, however, twelve loaves must be placed on the table. See:
http://www.atorahminute.com/2009-06-18)
If one has only one loaf of bread but has another frozen loaf in the freezer, can the frozen loaf be used together with the first loaf as Lehem Mishneh? According to the Ohr LeSion, the frozen loaf may be combined with the other one to form Lehem Mishneh. The rationale is that since if one were to separate Hallah from the frozen bread it would be considered to be a valid separation, and additionally, frozen bread has the same rules concerning the contracting of ritual impurity as does non-frozen bread, this shows that frozen bread is considered to be bread.
As such, he considers that frozen bread may, indeed, be combined together with the edible loaf to form Lehem Mishneh.
(See Ohr Lesion, Heleq 2, Ch. 21, Oth 2)
