Step #1 preheat your trusty oven to 250 degrees F.
Step #2 Generously butter heavy large baking pan.
Step #3 Mix warm popcorn & almonds in prepared pan.
Step #4 place this in oven while preparing syrup.
Step #5 mix brown sugar, butter & corn syrup in heavy medium saucepan.
Step #6 Whisk over medium-low heat until sugar dissolves & butter melts.
Step #7 Attach clip-on candy thermometer to side of pan.
Step #8 Increase heat to high & boil without stirring until thermometer registers 255 degrees F, every once in awhile brushing down sides of pan with wet pastry brush, about 4 mins.
Step #9 remove this from heat.
Step #10 stir in the vanilla extract, salt & baking soda (mixture will bubble).
Step #11 slowly pour syrup over popcorn & nuts completely.
Step #12 bake this until caramel feels dry, stirring frequently, about 1 hr 30 mins.
Step #13 remove this from oven.
Step #14 Using metal spatula, scrape mixture from bottom of pan to loosen.
Step #15 Cool completely in pan.
Step #16 (Can be prepared 1 week ahead.
Step #17 store this in airtight container at about room temp.