I like to rub out my pastry boards with Vanilla extract, a pinch of sugar, and a dash of finely chopped cloves....
Actually, I have never run across this question before. I suspect that a pastry board is exactly the same as a cutting board except you don't use it for cutting, right? I would go with either a light coat of mineral oil or, in this case, a coat or two of 1lb cut shellac. FWIW.
I wouldn't use any oil at all on a pastry board. Cutting board - mineral oil; Pastry board - flour .
If I were to add a finish I might use a 1.5lb cut of dewaxed blonde shellac and apply a couple of coats - enough to seal the wood but not enough to build a finish. I would then rub out the shellac with 000 (not 0000) steel wool to burninsh the surface.
I was given a pastry board that came from Chef's catalog. It came with a note that said the board had to be seasoned before using. They recommended a non vegetable oil, or parafin wax as in canning (heat it to melting and rub on) They said never immerse in water, but to just wipe off after each use.