Line a large baking sheet with parchment paper. Combine butter, sugar, and corn syrup in a small saucepan over medium heat,cook stirring occasionally, until butter has melted. Bring to a boil, add condensed milk and continue to boil 5 minutes, stirring to prevent scorching. Remove from heat and stir in vanilla. Place popcorn in a large bowl. Pour butter mixture over popcorn and stir gently to coat completely. Set aside until mixture has cooled enough so that it's still sticky but won't melt candy 3-5 minutes. Toss in peanuts, toffee bits, and white chocolate chips. When popcorn mixture is cool enough to handle grease hands and form to 2 inch balls. Sprinkle with salt if desired. Store in airtight container.