Adjust oven racks to the upper-middle and lower-middle positions and preheat the oven to 450°F (230°C). Lightly grease a baking sheet with coconut oil.
In a small mixing bowl, combine 0.25 cup (1 oz / 28 g) almond flour, 0.5 tsp granulated garlic, 0.5 tsp chili powder, and 0.5 tsp sea salt.
Whisk to combine and set aside.
Using a mandoline, slice the zucchinis approximately 0.125 inch (3 mm) thick.
Arrange the slices on the greased baking sheet in a single layer.
Bake until the zucchini releases most of its moisture but is not burnt, usually about 10 to 12 minutes.
Remove from the oven.
In a Dutch oven, heat 2 tsp (0.33 oz / 9 g) coconut oil over medium-high heat until shimmering.
Add the chopped onions, minced jalapeños, and 2 tsp cumin.
Cook, stirring occasionally, until the vegetables are lightly browned, about 6 minutes.
Stir in the canned tomatoes with their juices and cook until most of the liquid has evaporated, approximately 8 minutes.
Stir in the flour (reserve the tapioca flour for later).
Season with 0.5 tsp sea salt and 0.5 tsp pepper and cook for 1 minute.
Slowly whisk in 3.5 cups (28 oz / 794 g) chicken broth and bring the mixture to a boil.
Reduce heat to medium-low and simmer until slightly thickened, about 3 minutes.
Add the chicken breasts to the pot and bring to a simmer.
Reduce heat to low, cover, and cook until the chicken registers an internal temperature of 160°F (71°C), typically 10 to 15 minutes.
Remove chicken to a carving board, let cool slightly, then shred into bite-size pieces.
In a small bowl, whisk the 6 tbsp (1.6 oz / 45 g) tapioca flour into the 0.125 cup (1 oz / 30 ml) coconut milk until smooth.
Remove the Dutch oven from the heat.
While the sauce mixture is still hot, stir in the coconut milk/tapioca slurry.
Add the shredded cheese, a handful at a time, stirring until melted and thickened.
Stir in the cilantro and the shredded chicken.
Assemble the casserole: Place half of the baked zucchini slices into a 13x9-inch baking dish.
Top with half of the chicken mixture.
Repeat with the remaining zucchini and the remaining chicken mixture.
Sprinkle the reserved almond flour spice mixture over the top and spray lightly with oil spray.
Bake on the upper-middle rack until the sauce is bubbling around the edges, about 15 to 20 minutes. Allow the casserole to cool slightly before serving.
Don't Skip the Pre-Bake: Zucchini is about 95% water. If you skip the step of roasting the slices before assembling, that liquid will release into your casserole, turning your rich sauce into soup. You want the zucchini "dry" to the touch but not brown.
Shredding Hack: If you want to shred your chicken breasts in seconds, toss the warm cooked chicken into a stand mixer fitted with the paddle attachment.
Mix on low for 15–20 seconds, and you’ll have perfectly shredded meat without the fork fatigue.
Manage the Heat: The heat in this dish comes mainly from the jalapeño seeds and ribs. For a family-friendly version, carefully scrape out all the white membrane and seeds before mincing. If you love spice, leave a few seeds in!
Smooth Sauce Secret: When adding the tapioca starch slurry and dairy-free cheese, make sure your pan is off the heat. If the sauce boils while you are adding these thickeners, the texture can become gummy or the oils might separate. Residual heat is plenty to melt the cheese.
Meal Prep Friendly: This casserole tastes even better the next day after the flavors have had time to meld. You can assemble the entire dish ahead of time, cover it tightly, and refrigerate it for up to 24 hours before baking. Just add 5–10 minutes to the final bake time if it’s coming straight from the fridge.
