Page 121 - Peter Randall "The Craft of the Knot.."

STEP 1 Start as you would to tie a regular Bowline, then use the
running end to make a second loop.

STEP 2 Continue the same as you would with a Bowline.

STEP 3 Finish by making the final tuck.

With the Portuguese Bowline, you’ll have two loops that can be
adjusted in relative size after the loop is tied, but the strain on both must

be equal.