Prepare the vinaigrette by whisking together the shallots, mustard, and red wine vinegar in a small bowl.
Drizzle in the olive oil, whisking constantly, until the dressing comes together. Season to taste with salt and pepper.
If you are using bacon slices, stack together and cut into ¼-inch slices.
Sauté bacon slices or lardons in a nonstick skillet over medium-high heat, until crispy, 8-10 minutes.
Remove bacon from pan and set aside on a paper towel-lined plate.
Add baguette cubes to the pan, turning the heat down slightly. Sauté until croutons are golden brown, about 5 minutes, stirring frequently. Season baguette cubes with salt and pepper to taste.
To prepare the salad, rinse frisée lettuce and pat dry.
Toss lettuce with half of the vinaigrette, then divide among four plates.
Bring a large saucepan or deep skillet of water to a simmer.
Crack each egg into a small bowl by itself, then hold each bowl just over the simmering water and tip the egg in. Stir the water a bit with a spoon to make sure the eggs aren’t sticking to the bottom of the pan.
Cook for 3–4 minutes, depending on how runny you like your poached eggs.
Remove eggs with a slotted spoon and place either directly on each salad plate, or, on a paper towel-lined plate so you can remove some of the moisture before adding to your salad.
Top each plate with crispy bacon and croutons. Serve with remaining vinaigrette drizzled on top.
Notes
Note on Frisée Lettuce: Frisée is a member of the chicory family (like endive and escarole), and has a light peppery flavor. It is sometimes called curly endive. Frisée has a lacy texture that combines nicely with other greens, and is great in sandwiches too. Its texture really stands up to this salad, but if you can’t find frisée, look for other hardy greens such as escarole, radicchio, or endive. Be sure to dry frisée well after rinsing because water can really stick to its frizzy leaves.Tips for Poaching Eggs: Some people recommend adding a teaspoon of vinegar to the boiling water, which does help to keep the egg whites together a little better (and doesn’t make them taste like vinegar!). Also, creating a vortex in the water by stirring it before you add the egg does also help keep the egg together—but, it is difficult to do this when you are poaching multiple eggs at once. If you’re just poaching one, definitely try it! Deeper pots are also generally better to use than shallow pans, but again, it can be difficult to find a wide, deep pan for poaching multiple eggs (and that’s a ton of water used). Finally, poached eggs work best with the freshest eggs possible since the white tends to become more liquidy as eggs age.How long to poach eggs? You can decide how runny you want the yolk of your poached egg. I like a 3-minute poach, because the yolk is nice and runny. As you cut into it, the yolk mixes in with the vinaigrette, which then coats every bite of your salad. But you are certainly welcome to poach your egg for longer (around 4 minutes) if you like a thicker yolk!