Rice Krispie Treats, with brown butter and vanilla

This our family's favorite rice krispie treat recipe. Browning the butter and adding the vanilla makes them have a little extra je ne sais quoi that makes them irresistible.  Adapted slightly from Mel’s Kitchen Cafe.

INGREDIENTS
 8 tablespoons (1 stick) butter
16 ounces large marshmallows or 6 1/4 cup mini marshmallows
1 teaspoon pure vanilla extract
Pinch coarse, kosher salt or sea salt
9 cups crisp rice cereal (i.e. Rice Krispies)
Sprinkles (optional)

DIRECTIONS
Butter or spray the bottom and sides of a 9X13-inch pan. Set aside.

In a large saucepan, melt the butter on low heat and let it cook until the solids start to turn golden brown and it smells caramelly and fragrant.

Add the marshmallows and cook on low, stirring constantly until essentially all melted.  Add the vanilla and salt and stir to combine. Remove the pan from the heat.  In a large bowl put half the rice krispies, then scrap in the marshmallow butter mixture, and then add the other half of the cereal.   Stir until evenly combined. Scrape the mixture into the 9x13 pan and using lightly greased spatula, lightly press the mixture into the pan (mashing them too hard and you'll end up with very firm rice krispie treats - so use a gentle hand if you want them chewy).  Add sprinkles on top if desired.  Let cool before slicing into squares.