"Whomever Allaah feeds, should say:
اللَّهُمَّ بَارِكْ لَنَا فِيهِ وَأَطْعِمْنَا خَيْراً مِنْهُ
O Allah, bless us in it and provide us with better than it.
Allaahumma baarik lanaafeehi wa 'at'imnaa khayranminhu.
...and whomever Allaah gives milk to drink, should say:
اللَّهُمَّ بَارِكْ لَنَا فِيهِ وَزِدْنَا مِنْهُ
O Allah, bless us in it and give us more of it.
Allaahumma baarik lanaa feehi wa zidnaa minhu.
At-Tirmithi 5/506. See also Al-Albani, Sahih At-Tirmithi 3/158.