Line a 13x18 sheet pan with parchment paper.
In a large pot, melt butter over medium heat. It will melt, then foam, then turn clear golden and finally start to turn brown and smell nutty, which should take about 2-3 minutes.
Remove from heat and stir in the marshmallows, stirring until everything is melted. Add in the vanilla extract, sea salt and rice krispies, tossing everything to combine. Transfer to the pan and pack tightly.
Let treats cool for an hour and then cut into 2 inch circles.
Place the chocolate and coconut oil in a microwave safe bowl. Microwave in 30 second intervals, stirring in between and repeat until the chocolate is melted. Use two forks to dip each rice krispies treat into the melted chocolate then place onto parchment paper. Place in fridge for 10 minutes to harden.
Break the cookies in half and then separate all of the pieces from one another so you now have "bat wings". Scrape off the frosting and put in a ziploc bag. Cut off the tip of the bag so you can use to "glue" everything together.
Pipe frosting on back of eyes and place on top of the rice krispies treats. Pipe the frosting onto the back corners of the broken cookie pieces and press two cookies on the back of the rice krispies treats to form wings. You now have bat treats.