Bring a pot of water to a boil and cook your potatoes until fork tender. Drained and set aside to cool slightly for 2-3 minutes
Preheat your oven to 180C/350F.
In a different pot, add in the milk, herbs and garlic. Bring it to a simmer and keep it simmering for 3-5 minutes for the ingredients to release its flavours into the milk. Set aside.
With a potato ricer or some sort of mesh, mash your potatoes. Add in herb infused milk and mix well until combined. Add in the butter and mix well until combined. Season to taste and transfer the mash into a casserole dish.
Top the casserole with cheese and bake until the cheese is melted and golden brown. Remove from oven and let cool slightly before enjoying!