this is from a time life cookbook of Spain and Portugal 1969

Migas
a national Spanish dish with regional variants throughout the Peninsula.
Migas are fried bread chinks, referred to in English by the French word croutons, which does not do justice in either language to the dish that isprepared in Spain. It is said that migas constitute the most ancient dish in the whole Peninsula, tracing back to early Iberian or Celtiberian cooking.
That is the way migas are prepared in Aragon today, from two-day-old bread that has been cut or broken into very small chunks about the size of chick-peas and soaked overnight in a wet, salted cloth. In the morning, garlic is heated in oil and then discarded and the migas are dropped in the oil. Bits of ham are sometimes added and the bread is left to brown until it is the color of rust. Migas are eaten in all of Spain with almost anything from fired eggplant to hot chocolate.


migas de pastor
1 lb/500g stale Spanish white bread
Salt
6 Tbsp lard or olive oil
1-1/4 C / 150g diced bacon
4 cloves of garlic, sliced

Dice the bread the day before you want to use it. Place it in a bowl and sprinkle over some slightly salted water, do not let it get too wet. Mix well and leave overnight.
Heat the lard or oil in a cast-iron skillet and fry the bacon. Add the soaked bread to the skillet and turning with a wooden spoon, fry until golden.
They are often served with chilled white grapes or chorizo or other spicy sausage or fried eggs.

If, as I suspect, you're translating a menu, in a case like this the best option (in many cases) is to leave it as is and add the shortest description possible.

Migas are as described above, definitely. Or,

I take old bread, rub the surface with garlic, shave off slices, and repeat the processs until there are enough.

Then it's up to the chef. Slightly fried with chorizon, ham, bacon, etc....or just fat and maybe a herb or two.

To sum up, if it's a menu, I'd leave it as is, ask the restaurant the ingredients and method and try and come up with the shortest possible description.