Directions: 1. For grainy mustard vinaigrette, in a small saucepan stir together mustard, vinegar and olive oil. Bring to boil, stirring to combine. Reduce heat, keep warm until serving.
2. Grease 4 cups of an egg poaching pan with cooking oil. Place poacher cups over pan of briskly boiling water (water should not touch bottom of cups). Reduce heat to simmering. Break one of the eggs into a measuring cup. Carefully slide egg into a poacher cup. Repeat with remaining eggs.
3. Cook covered, for 6 to 9 minutes, or until the whites are completely set and yolks begin to thicken but are not hard.
4. To serve: place spinach on 4 plates.
Loosen poached egg by running a knife around edge of each poacher cup; invert poacher cups and slip eggs onto spinach. Stir vinaigrette and pour over eggs. Season with salt and pepper.
Note: if you don't have an egg poaching pan, lightly grease a medium skillet. Add water to half-fill the skillet. Bring water to boil, reduce heat to simmering (bubbles should begin to break the surface of the water). Break one of the eggs into a measuring cup. Carefully slide egg into simmering water, holding the lip of the cup as close to the water as possible. Repeat with remaining eggs, allowing each egg an equal ammount of space. Simmer eggs, uncovered for 3 to 5 minutes, or until the whites are completely set and yolks begin to thicken but are not hard.
Serve as mentioned above.