Cake:

1. Place butter in a small, heavy saucepan over medium heat until melted. Cook, stirring occasionally until the milk solids on the bottom of pan begin to brown and the butter has a nutty aroma, about 10 to 15 minutes. Transfer the butter, including the browned bits at the bottom of pan, to a glass bowl. Place in freezer about 20 minutes, or until it begins to firm.
2. Preheat oven to 350?F. Grease and flour two 9-inch OR three 6-inch cake pans; set aside.
3. Stir together flour, baking powder and salt in a large mixing bowl until combined.
4. Beat browned butter, sugar and brown sugar together in a large mixer bowl on medium speed about 3 to 4 minutes until light and fluffy, scraping sides and bottom of bowl occasionally. Add vanilla, eggs and egg yolks, one at a time with mixer on lower speed.
5. Add half the flour mixture and milk to mixer bowl; mix on low speed until blended; repeat. Mix batter on medium speed 20 to 30 seconds until mixture is blended, scraping sides and bottom of bowl.
6. Pour batter evenly into pans. Bake for 28 to 32 minutes for 9-inch pans or 23 to 26 minutes for 6-inch pans, or until a wooden pick inserted into center comes out clean.
7. Let cool on a wire rack for about 5 minutes before removing cakes from pans. Let cakes cool completely, approximately 1 hour.

Caramel Popcorn:

1. Preheat oven to 250?F. Line a 15 x 10-inch rimmed baking sheet with parchment paper. Stir together popcorn and peanuts; spread out on baking sheet; set aside.
2. Melt butter in a medium saucepan over medium heat. Stir in syrup and brown sugar. Increase heat to medium-high. Heat to boiling, stirring constantly. Boil about 4 minutes.
3. Remove from heat; immediately stir in salt, baking soda, cinnamon and vanilla. Mixture will foam. Pour sauce over popcorn mixture; stir to evenly coat popcorn and peanuts. Spread out in an even layer. Bake 45 minutes, stirring every 15 minutes. Remove from oven and let cool. Break up caramel corn as needed when completely cool.

Salted Caramel Sauce:

1. Combine sugar, syrup and water in a small saucepan. Bring to a boil over high heat, stirring occasionally. Reduce heat to medium and continue cooking until mixture turns to a medium amber colour, about 10 minutes. (Mixture should reach 350°F on a candy thermometer.)
2. Remove from heat; carefully stir in cream. (Mixture may bubble up a bit.) Stir in butter until melted. Stir in salt.
3. Note: If sauce is too thick after adding cream and butter, heat over low heat until smooth, stirring occasionally.
4. Transfer sauce to a microwave-safe container. Chill until cool and thickened.

Peanut Butter Frosting:

1. Beat butter and cream cheese together in a large mixing bowl until smooth. Add peanut butter; mix until smooth.
2. With mixer on low speed, gradually add remaining ingredients. Mix on medium speed until smooth. Add more milk or powdered sugar as needed for desired consistency.

Assembly:

1. Place one cake layer on serving plate. Frost top with frosting. Place remaining cake layer on top of first layer. (Add third cake layer if using 6-inch pans.) Frost sides and top with frosting.
2. Heat Salted Caramel Sauce just to room temperature. Spoon on top of cake and drizzle down sides. Mound Caramel Popcorn atop cake.

Recipe Tips:

1. Salted Caramel Sauce may be made up to one week in advance, and stored in refrigerator.
2. Recipe requires only about two-thirds of Caramel Popcorn.