Grease a 9" x 13" baking pan. In 5-qt dutch oven, over low heat, cook marshmallows, vanilla milk chips, and butter until melted and smooth. Remove from heat; stir in popcorn, peanuts and vanilla and mix until well blended. Press mixture firmly into prepared pan; sprinkle with gumdrops, gently pressing gumdrops into the popcorn mix. Let stand at room temp about 1 hour before cutting. Store in tightly covered container.