1cupoat flourif the oat flour looks coarse, grind it in a coffee grinder until fine
To make the oat flour pasta dough, combine the semolina and oat flour in the bowl of a stand mixer and stir with the paddle attachment, adding the egg yolks, salt and water as needed on low speed until the pasta dough just comes together.
Switch to the dough hook and knead for a few minutes, until the dough springs back when touched.
Allow the dough to rest, wrapped in plastic for 30 minutes or so before rolling out.
If you can't find oat flour, grind some oats in a spice grinder until very fine, or just skip it and use all purpose flour