1¼cupsdried whole green lentilsor small brown lentils like French du Puy
½medium yellow onionfinely chopped
1medium jalapeñoseeded and finely chopped
3tablespoonsextra-virgin olive oil
1medium lemonjuiced (about 3 tablespoons)
½teaspoonkosher saltplus more to taste
2tablespoonsfresh parsleychopped (for garnish)
Instructions
Make the senafich:
Grind the brown mustard seeds to a fine powder in a spice grinder or mortar and pestle. About 1 minute in a grinder, or 3 to 4 minutes by hand. Transfer to a small bowl and add the salt.
Stir in the olive oil. Whisk in 3 tablespoons of just-boiled water and let sit for 2 minutes. The mixture will thicken and the sharp raw bitterness will mellow slightly. Whisk in 1 more tablespoon of hot water until you have a saucy, pourable consistency. It should be looser than Western mustard, more like a thin dip than a spread.
Cover and refrigerate at least 2 hours, ideally overnight. Fresh-ground senafich tastes one-note sharp; after a night in the fridge it tastes complex and rounded. The rest is the part you plan for. Senafich keeps 3 days refrigerated.
Cook the lentils:
Pick over the lentils and discard any debris. Rinse well under cold water. Bring a large saucepan of water to a boil, plenty of water like pasta. Add the lentils and cook 25 to 30 minutes until just tender but still holding their shape. Taste at 22 minutes; you want them to have a little resistance, not be mushy. Drain immediately in a colander.
Spread the lentils on a sheet pan or transfer to a wide bowl to cool quickly. Once at room temperature, cover and refrigerate until fully chilled, at least 1 hour.
Assemble:
Transfer the chilled lentils to a large bowl. Add the onion, jalapeño, olive oil, lemon juice, and 2 teaspoons of the senafich. Toss gently to combine. Taste; add more senafich for sharpness, more lemon for brightness, more salt as needed. Start conservative with the senafich and build up.
Serve cold, garnished with fresh parsley. Pass extra senafich at the table for anyone who wants more sharpness.
Notes
The senafich needs time. Make it at least 2 hours ahead, preferably the night before. Fresh-ground mustard tastes one-note sharp; rested mustard tastes complex and rounded.
Senafich yields about ¾ cup. The salad uses 2 to 3 teaspoons. Save the rest for the table or for future batches.
Brown mustard seeds are the same seeds Indian cooks use for tempering. The Indian spice aisle at any mainstream grocery store, Whole Foods, or an Indian grocery is the cheapest source. Yellow mustard seeds work as a substitute and produce a milder, less pungent senafich.
Don't overcook the lentils. Cold salad means the lentils need to hold their shape through chilling and tossing. Pull them while they have a little bite.
Make-ahead friendly. The senafich keeps 3 days. The cooked lentils keep 3 days undressed. Dress just before serving for best texture.
Dressed salad keeps refrigerated up to 2 days. The lentils absorb the dressing as it sits, so toss with a drizzle of olive oil and a squeeze of lemon before serving leftovers. Serve cold or at room temperature; do not reheat.