No-bake Chocolate Cookies

1 stick butter
½ cup evaporated milk
1 ½ sugar
3 tbsp cocoa
½  cup peanut butter
1 tsp vanilla
2 cups rolled oats

Melt butter. In a stovepot, add butter and milk to sugar and cocoa. Stir together. Boil on low for 1 minute. Mix in peanut butter and vanilla. Pour mixture over oats. Drop onto waxed paper. Refrigerate until firm.