Melt the butter in a small skillet over medium heat, then cook, swirling occasionally, until nutty smelling and the solids are nicely browned, about 4 minutes. Transfer to a small bowl or measuring cup.
Line a baking sheet with parchment paper and spray lightly with cooking spray.
Mix the maple syrup, sugar and 1 teaspoon salt together in a small bowl.
Put the oil and 3 or 4 popcorn kernels in a large pot (at least a 6-quart) with a lid. Cover the pot and turn up the heat to medium-high. Wait until you hear one of the kernels pop, then uncover the pot and add the maple syrup mixture and the popcorn kernels; quickly stir everything together, then replace the lid.
Cook the popcorn until the kernels begin popping, then reduce the heat slightly. Cook, shaking often, until the rate of popping starts to slow, 2 to 3 minutes. Do not wait for all of the kernels to pop, or it will burn! Uncover the pot and stir in the brown butter, pistachios and candy.
Pour the popcorn out on the prepared parchment to cool, 15 to 20 minutes. Transfer to a serving bowl, leaving behind any unpopped kernels.