Dear _________,
What a treat it was to be invited to your home for dinner. You are both such fabulous cooks, and the way each dish was presented was a bit like viewing great works of art. We really enjoyed ourselves, and would like to reciprocate your kindness. Although my culinary talents are quite limited, I do make an excellent brunch. Bob and I are having a few guests over for brunch this coming Sunday, and we’d be delighted if you would join us. It will be a casual, relaxed, and lively gathering.
(YOUR NAME HERE)