6ouncesthick-cut baconcut into 1/2-inch pieces (about 6–7 slices; I recommend buying the strips directly from the butcher case in the meat department versus prepackaged)
3/4poundbaby red potatoesquartered (new potatoes that are smaller than a golf ball)
2tablespoonswhite wine vinegarplus additional to taste
2 1/2tablespoonsstone-ground brown grainy mustard
1teaspoonkosher saltplus additional to taste
1/2teaspoonground black pepperplus additional to taste
2cupspeasfresh, or frozen and thawed
1/4cupchopped fresh chives
Cook the lentils according to the package instructions until al dente, adding a big pinch of salt to the pot as they cook—they should be tender but not mushy and have a pleasant chew. Drain and place in a large mixing bowl.
In a large skillet over medium-low heat, cook the bacon until it is crisp and the fat has cooked off, about 8 minutes. With a slotted spoon, remove the bacon to a paper-towel-lined plate and lightly pat dry. Leave the bacon drippings in the skillet.
Add the potatoes, increase the heat to medium, and sprinkle with salt and pepper. Cook, stirring occasionally, until the potatoes are tender on the insides and crisp and golden on the outsides, about 12 to 14 minutes. Remove the pan from the heat, then add the vinegar and mustard. Stir to coat the potatoes in the vinegar, mustard, and drippings, then scrape all of the skillet contents into the bowl with the lentils. Add the peas.
Stir to combine, then give the salad a taste. Add salt and pepper and/or a splash of vinegar (for more tanginess) as desired. (I added a bit of all three.) Add the chives. Enjoy immediately or refrigerate for up to 1 day. Serve at room temperature.
Refrigerate leftovers for up to 3 days. Enjoy at room temperature.
The entire salad can be made 1 day ahead (including the dressing). You can also make the lentils an additional 1 day in advance.
Source: Adapted from Dining In by Alison Roman, a cookbook I adore and highly recommend.