Preheat oven to 300 degrees. Line a large baking sheet with foil, cut the butter into pieces and place on the baking sheet. Once the oven has preheated, place the baking sheet in the oven to melt the butter, watch closely, you do not want to brown the butter. Once melted, remove from the oven. In a small bowl, mix together the brown sugar, chili powder and vanilla. Using your stand mixer and wire whisk attachment, beat the egg whites until soft peaks form, add 1/4 teaspoon salt, mix well. Add the sugar mixture one tablespoon at a time on medium high, when you have incorporated all of the sugar mixture, beat on high speed until glossy and thick. Gently fold in the pecan halves until well mixed. Spread pecans over the melted butter, do not mix. Cook for 20 minutes, remove from the oven and stir the nuts, those on the edge should come to the middle and those in the middle move to the edge, the butter will now start coating the pecans. Cook an additional 15 minutes, stir again, sprinkle with remaining 1/4 teaspoon salt. Continue to cook and stir in 15 minute increments (45 minutes to 1 hour).. When the nuts are golden brown and the butter has glazed all of the nuts, remove from the oven and spread on a piece of foil to completely cool.

Store in an airtight container - the nuts can be stored at room temperature for 3 weeks.