Sweet Potato Casserole

A low FODMAP sweet potato casserole of maple-sweetened mash with butter, lactose-free milk, and egg under a gluten-free pecan streusel.

Prep 20 min

Cook 45 min

Serves 8

Gluten-freeVegetarian

Ingredients

For the filling:

• 600g (about 1.3 lb) orange sweet potato, peeled and cut into 1-inch cubes (about 75g per serving; boiled sweet potato weighs about the same as raw)
• 2 tablespoons (30g) unsalted butter
• 3 tablespoons (45ml) lactose-free milk
• 2 tablespoons (30ml) pure maple syrup
• 1 large egg, lightly beaten
• 1 teaspoon vanilla extract
• 3/4 teaspoon ground cinnamon
• 1/4 teaspoon ground nutmeg
• 1/4 teaspoon salt

For the pecan topping:

• 1/2 cup (60g) pecans, roughly chopped
• 1/4 cup (30g) gluten-free 1:1 flour blend
• 1/4 cup (50g) packed light brown sugar
• 2 tablespoons (30g) cold unsalted butter, cut into small cubes
• Pinch of salt

Instructions

Cook the Sweet Potato

1. Heat the oven to 375°F (190°C). Lightly grease an 8-inch square baking dish or a similar 6-cup dish.
2. Put the sweet potato cubes in a saucepan, cover with water, and boil until fork-tender, 12 to 15 minutes. Drain well and return to the pan for a minute to steam off any extra water.

Make the Filling

1. Mash the sweet potato with the butter, lactose-free milk, maple syrup, cinnamon, nutmeg, and salt until smooth.
2. Let it cool for about 5 minutes so it won't cook the egg, then stir in the beaten egg and vanilla.
3. Spread the mash evenly into the prepared dish.

Top and Bake

1. In a small bowl, stir together the pecans, flour, brown sugar, and salt. Add the cold butter and rub it in with your fingertips until the mix looks like coarse crumbs.
2. Scatter the topping over the sweet potato.
3. Bake for 25 to 30 minutes, until the topping is golden and the filling is set (an egg-based dish is done at 160°F / 71°C). Rest 5 to 10 minutes before serving.

Tips & Substitutions

• Keep the sweet potato to 75g per serving. Monash rates orange sweet potato low FODMAP at about ⅓ cup (75g), with larger portions moderate and much larger portions high. Cut the finished dish into 8 equal portions to keep each at the tested serve.
• No marshmallows needed. The pecan streusel gives a sweet, crunchy top; if you add marshmallows, check the label for honey or high-fructose corn syrup.
• Make it egg-free. Leave out the egg and stir 1 tablespoon of the GF flour blend into the warm mash instead. It sets a little softer but slices fine after resting.
• Watch the pecan portion. Pecans are low-FODMAP at about 15 nut halves (30g) per serving. This recipe uses about 7.5g per portion.
• Swap to walnuts if you prefer. Walnuts work in the topping at the same amount (low FODMAP at about 15 nut halves, 30g); look up walnuts in the FODMAP Foods app to see how the rating changes with portion size.
• For a dairy-free version. Use a plant-based block butter and a low-FODMAP milk like almond or a lactose-free oat milk in place of the dairy. The topping still crisps.

Why This Works

Sweet potato at the tested serve. Eight equal portions hold about 75g of sweet potato each, Monash's low FODMAP serve; larger heaps are where the fructans add up.

Maple syrup instead of honey. Honey is low FODMAP only at about ½ teaspoon (4g). Maple syrup is low FODMAP at 1 tablespoon, and each portion here gets under 1 teaspoon.

A pecan topping in a small portion. Pecans test low FODMAP at about 15 nut halves (30g), and the topping supplies about 7.5g per portion.

Gluten-free flour in the streusel. Wheat flour brings fructans. A GF 1:1 blend (one without added inulin or chicory root) binds the crumb without them.

Storage

Cover and refrigerate leftovers for up to 3 to 4 days. Reheat individual portions in the microwave, or warm the whole dish covered in a 350°F (175°C) oven until hot. It freezes for up to 2 months; thaw overnight in the fridge before reheating, though the topping softens a little. Divide leftovers into the same 8 portions.