Line a cookie sheet with parchment paper. Set aside.
In a microwave safe bowl melt the milk chocolate chips on medium heat for about 1 minute, check the chocolate by stirring it, if not melted you can turn on again for 30 seconds. Check and stir again. Repeat if necessary. The chocolate should be smooth.
In a second microwave safe bowl combine the shortening and peanut butter chips and microwave on medium heat for 1 minute, check the peanut butter chips by stirring it, if not melted you can turn on again for 30 seconds. Check and stir again. Repeat if necessary. The peanut butter chips should be smooth.
Spoon each one alternately in lines on the pan you line with parchment paper. Just add it randomly, doesn't need to be any rhyme or reason to it. Continue until all the melted chocolate and peanut butter is on the sheet. Now take a butter knife and start to pull it through the colours to create a marble effect. I like to do mine in lines and pull straight through. I like the look of it. But design yours any way your little heart desires.
Toss the skor toffee bits on top.
Place the cookie sheet in the fridge for about an hour to set up.
Remove from the fridge and break into pieces.
Serve with a big old chocolate and peanut butter smile!