Add onion to the milk to soak while you are working the flour and butter.
Cut butter into flour and salt until it’s the texture of cornmeal.
Combine the rest of the ingredients and add to the flour mixture.
Stir until mixture forms a ball (if dough is too sticky, add a little more flour) but avoid overworking in order to keep the crackers tender.
Divide the dough into thirds and roll out onto a well-floured surface.
Roll until thin, about 1/16” to 1/32”.
Cut into desired shapes and place on a lightly greased cookie sheet.
(Do-ahead idea: Cut cookies into shapes, and arrange them on layers of waxed paper in a freezer container and freeze until ready to bake. This can be done several weeks in advance of NTBMO.)
Prick crackers with a fork.
Bake in a 450°F oven for 5-8 minutes, or until light brown around the edges.
Notes
This dough can be made ahead of time and frozen until ready to bake.