KetoFLEX 12/3 Kitchen is all about mackerel this month, the under-utilized SMASH fish that is an excellent source of protein, high in omega-3 fatty acids, and other micronutrients, including B12, vitamin D, calcium, selenium, and magnesium. Our recipe for Mackerel Mushroom Casserole featured below uses carefully sourced, canned mackerel, which can easily become a staple in your pantry for a quick, nutritious meal.

This month’s recipes for Mackerel Mushroom Casserole, Mackerel Patties, and Vegan Creamy Dill Sauce are available to members of our PreCODE and ReCODE programs.

Mackerel Mushroom Casserole


The fusion of coconut milk with garlic, lemon, dill, and capers is reminiscent of the smooth, creamy flavor of chicken piccata or Marsala, but our version is dairy-free and loaded with omega-3s. Enjoy with a green salad or spoon it on top of your favorite keto crackers or toasted keto bread.

Yield: six servings


● There are many types of mackerel, and sourcing is important. Our preferred brands are Bar Harbor (sourced from Latvia), Vital Choice (sourced from Portugal), and Patagonia Provisions (sourced from Spain) because they are sustainably sourced and wild-caught. The latter recommendation is slightly confusing because we generally warn against Spanish and king mackerel, which are high in mercury. Patagonia Provisions sources from Spain, but only small fish from the Atlantic side are considered safe. All of these options have BPA-free cans, except Patagonia Provisions, which offers BPA and BPS-free cans. See for more information on safe and sustainable sourcing.   

● Bar Harbor mackerel is an alternative for this recipe. You will need to use only three cans of their 6.7 oz. Mackerel and add two extra tablespoons of olive oil to the onion mix.

● Be sure to use canned coconut milk that does not contain any additives like guar gum. 

● This recipe also works well with other types of mushrooms.


● 5 (4.4 oz) cans of wild caught mackerel in olive oil (preferably extra virgin), drained. We used the Patagonia Provisions Lemon Caper Mackerel. 
● 8 oz of shiitake mushrooms, sliced
● 2 tbsp high polyphenol extra virgin olive oil (EVOO)
● 6 green onions, chopped
● 2 tsp lemon zest
● 2 tbsp fresh lemon juice
● 2 tbsp fresh dill, chopped
● 2 tbsp capers, drained & rinsed
● ¼ cup nutritional yeast or 1/3 cup shredded manchego cheese
● Salt and pepper to taste


1.  Preheat the oven to 400 degrees Fahrenheit.

2. Heat olive oil in a small pan and add green onions. Sauté onions until soft, then add garlic and continue to sauté for another two to three minutes. Remove the pan from the heat.

3. Add lemon zest, lemon juice, dill, and capers to the pan and stir and set aside.

4. Drain the oil off the mackerel and place them in a single layer at the bottom of an 8″ x 8″ casserole dish. Toss in any capers left in the can.

5. Spoon your onion/garlic mixture evenly over the mackerel.

6.  Layer your mushrooms evenly on top of the onion/garlic mix.

7. Pour the coconut milk over the mushrooms and sprinkle nutritional yeast or cheese evenly over the casserole.

8. Bake for 20 minutes, then increase heat to 425 for an additional six to seven minutes.


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