Line a baking sheet with aluminum foil; spray lightly with cooking spray. Reserve 2 tablespoons of almonds and sprinkle the rest evenly over the foil.
Combine brown sugar and maple syrup in a 2-quart saucepan over medium heat. Cook and stir until sugar is dissolved and caramel mixture comes to a full boil, about 10 minutes.
Preheat oven to 350 degrees F (175 degrees C).
Turn oven off once preheated; place prepared baking sheet in the oven to warm.
Attach a candy thermometer to the saucepan with the caramel mixture. Add butter. Cook, stirring occasionally, until the mixture reaches 300 degrees F (149 degrees C) or until a small amount dropped into ice water forms a hard, brittle strand, about 20 minutes.
Remove baking sheet from the oven and immediately pour the caramel mixture over the almonds. Spread evenly to about 1/4-inch thickness. Sprinkle remaining almonds and chocolate chips over open spaces. Spread chocolate evenly once melted. Let brittle cool completely, at least 30 minutes. Break into pieces.