Sift the flour into a large mixing bowl and blend in the eggs, mustard, cream, salt, and pepper.
Bring a large saucepan or stockpot of lightly salted water to a full boil. Set aside a shallow bowl or strainer lined with paper towels.
To make the spätzle, use a spätzle press, or simply press small spoonsful of dough through the holes of a colander, to make round noodle-like bits about an inch long. Drop the spätzle directly into the pot from the press or colander. When the spätzle rises to the surface, it is done. Do not overcook the spätzle; it should be al dente. Quickly remove the spätzle from the pot with a slotted spoon or strainer and drain in the bowl lined with paper towels.
In a frying pan, heat the butter and sauté the spätzle until light golden brown. Season with salt and pepper and garnish with chives.