Roasted Mustard Fish with Lentils and Veggies is Easy, Healthy, and Delicious

  • By Jess Dang
  • March 5, 2013

Mustard roasted fish over green lentils, peas, and spinach

I can’t believe there’s been only one lentil recipe on Cook Smarts so far. Now that’s what I call a travesty. I’ll fix this oversight today by sharing this super simple and healthy mustard roasted fish and lentils recipe. This meal is something you’d find at a fancy schmancy French restaurant for well over $15 / plate, but I’m going to show you how to replicate the same results in your own kitchen.

If you’ve never worked with lentils, they’re a great ingredient that just about every dietary group can enjoy. They can take on a lot of different flavors and are also full of fiber and protein. I keep both dried green or French lentils, which are almost black in color, in my pantry as they’re my favorites for flavor and texture. I’ll soak them the night before or the morning of cooking using a 3 to 1 water to lentils ratio. This short little step will significantly cut down amount of time it takes to cook them so is completely worth a bit of planning.

I love them paired with many different types of vegetables and proteins but a simple roasted fish seems like the perfect French choice. Today’s roasted mustard fish recipe is adapted from the Barefoot Contessa and uses classic French flavors – capers, mustard, shallots, thyme, and creme fraiche – to create a simple sauce that cooks with the fish. The result is an incredibly tender fish dish that pairs perfectly with our al dente lentils. 


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Easy Mustard Roasted Fish Recipe

This fish and lentils dish is something you’d find at a fancy schmancy French restaurant for well over $15 / plate, but I’m going to show you how to replicate the same results in your own kitchen.

Prep time: 20 min

Cook time: 15 min

Total time: 35 min

Serves: 4


  • Ingredients - Lentils
  • French or green lentils, dried – 1 cup
  • Garlic, minced – 4 cloves
  • Onions, diced – 1
  • Canola oil – 1 tbs.
  • Chicken / vegetable broth – 2 cups
  • Dried thyme – 1 tsp.
  • Frozen peas – ~4 oz. (1 cup)
  • Baby spinach – 4 oz.
  • Ingredients - Fish
  • Shallots, minced – 2 tbs.
  • Any type of fish (e.g., tilapia, halibut, salmon) – 4 4 to 6 oz. fillets
  • Dried thyme – ½ tsp.
  • Lemons, juice & wedges – 1
  • Capers (opt) – 1 tbs.
  • Dijon mustard – 1 tbs.
  • Crème fraiche – 1/4 cup



  1. Lentils – Give them a quick rinse, and soak in 3x the amount of water the night before or morning of cooking
  2. Garlic / Onions / Shallots – Prep as directed
  3. Fish – Rinse and dry with paper towels


  1. Preheat oven to 425 degrees
  2. Heat a >3.5 quart Dutch oven over medium-high heat. Add 1 tbs. canola oil and then minced garlic to heated oil. Add diced onions with a dash of salt. Sauté for 3 minutes, until softened and translucent
  3. Add drained lentils and then add 2 cups of stock if you soaked them overnight or 3 cups of stock if not soaked. Add 1 tsp. thyme and ½ tsp. kosher salt. Cover and bring to a boil. Simmer uncovered for 10 minutes if lentils were soaked, 25 to 30 minutes if not soaked
  4. Mix together ½ tsp. dried thyme, shallots, 1 tbs. lemon juice, capers, Dijon mustard, and crème fraiche with ¼ tsp. kosher salt
  5. Place fish into a baking pan. Sprinkle with salt and pepper and then cover with mustard mixture. Bake in oven for 12 to 15 minutes depending on thickness of fish
  6. When lentils have absorbed all their liquid, add peas and spinach. Cook for another 2 to 3 minutes and then season to taste with salt and pepper
  7. Enjoy fish with lemon wedges. The mustard / crème fraiche turns into a natural sauce. Serve over lentils
  1. Out of stock? Just use water and add a bay leaf
  2. If lentils still aren’t cooked after they’ve absorbed all the liquid, add more water or stock
  3. Vegetarian? Skip the fish and enjoy the lentils with a whole grain like barley or farro


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