Add 1 12-ounce bag frozen Brussels sprouts, ½ tablespoon olive oil, plenty of sea salt, and plenty of freshly cracked black pepper to medium mixing bowl. Stir or toss ingredients together until Brussels sprouts are fully coated in oil, salt, and pepper.
Remove basket from preheated air fryer. Transfer Brussels sprouts to air fryer basket and spread Brussels sprouts into single, even layer. Work in batches as needed to avoid overcrowding basket.
Return basket to air fryer. Air fry Brussels sprouts 10 minutes. After 10 minutes, pause air fryer and remove basket.
Shake basket to toss Brussels sprouts, then return basket to air fryer. Air fry Brussels sprouts another 6 minutes. Make maple-butter sauce simultaneously if using.
After 6 minutes, check Brussels sprouts. Continue air frying as needed, checking Brussels sprouts every minute, until outer leaves of sprouts are crisp and lightly charred.
For the Maple-Butter Sauce (Optional)
Add 2 tablespoons unsalted butter and 1 tablespoon maple syrup to microwave-safe bowl. Microwave butter and syrup in 30-second increments, whisking well after each burst, until syrup is hot and butter is melted or almost melted. Be careful not to burn either ingredient.
Once butter is melted and syrup is hot, carefully remove bowl from microwave. Add 1 teaspoon minced fresh garlic and ½ teaspoon salt, and whisk ingredients together until well incorporated.
To Serve
When Brussels sprouts are cooked as desired, remove basket from air fryer.
If using maple-butter sauce, transfer Brussels sprouts to bowl with sauce. Gently stir or toss Brussels sprouts to coat in sauce. Serve Brussels sprouts immediately.
If not using maple-butter sauce, serve Brussels sprouts immediately as desired.
Recipe Notes
Make it Dairy Free: Skip the maple-butter sauce, or use a plant-based butter to make your sauce.
Make it Keto: Skip the maple-butter sauce, or replace the maple syrup with a maple-flavored keto liquid sweetener.