01 -
Get your oven going at 350°F (175°C) and lightly coat a 9×13-inch baking dish with cooking spray.
02 -
Combine your cake mix with melted butter and eggs in a big bowl until you've got a sticky, thick mixture.
03 -
Take half your dough and push it down flat across the bottom of your greased pan.
04 -
Scatter your chocolate chips and toffee pieces over this base. Pour the condensed milk all over in a zigzag pattern.
05 -
Grab spoons of the leftover dough and dot them across the top, spreading gently but letting some filling show through gaps.
06 -
Pop in the oven for about 25-30 minutes until the edges turn golden and firm up.
07 -
Wait till it's totally cool before you cut it into squares.