In a large bowl, mix eggs, water, oil & grainy mustard. Slowly incorporate flour while sifting into egg mixture & season.
Bring a large pot of salted water to a boil. Put spaetzle dough through a ricer or a spaetzle machine directly into boiling water and cut off
Allow spaetzle to cook in water for 2-3 minutes. Remove spaetzle and plunge into an ice bath. When cooled down, remove from ice bath and dry on a clean towel.
Coat spaetzle with a little oil & refrigerate until ready to use.
To serve; In a large fry pan, over high heat , add a couple of tablespoons of butter and allow to brown. Add a little spaetzle and toss to coat. Allow to continue to cook until spaetzle becomes a little crispy. Season with salt & serve immediately.