Make cake according to directions on box.

Mix together butter, cream cheese, powdered sugar, and vanilla till smooth.

Dump cake out into a large mixing bowl. (It doesn't matter if the cake is warm or cool.) Smash it up and add the frosting, then the toffee bits. Stir till everything is well mixed.

Refrigerate till very cold.

Roll the mixture into balls. At this point you can freeze them and store them in ziplock bags for a few months.

Dipping: Melt your chocolate at half power in a glass bowl in the microwave. Stir every 30 seconds or so till the chocolate is smooth. 

Dip the cake bites into the melted chocolate one at a time. I either poke them with a toothpick, or use a baby spoon to dip them.  Shake off the excess and place the cake bite on waxed paper to set up.

Quickly sprinkle with toffee bits. (If the cake bites are frozen, they will set up very quickly.)

Repeat till all the balls are covered in chocolate.