I made a version of this yesterday along with two batches of cookies and cream fudge. 12 bags fudge so far. 
60 g butter, half a cup of sugar and 20 g glucose syrup 8 minutes 100’ speed 3 as per cookies and cream. Towards the end of the cooking time I added 1 tsp peppermint essence.
Then I added approximately 400 g of dark chocolate, some of it was chocolate mint and cooked a further 5 mins on 90’ speed 3. 
Finally I added 150 g mint galaxy and about 25 g dark choc mint. Mixed 30 secs reverse speed 3-4. 
Chilled cut into squares and in fridge. These are Xmas presents made early as I’m going away next week. 
Put 1 cup  milk into the thermi pan to clean it and 80’ 5 mins speed 6. OMG the best hot chocolate ever! 
Will let you know how it keeps, it’s bagged and in the fridge. I couldn’t get mint crisp bars at all when shopping yesterday.