Method

Peel the potatoes and slice any large potatoes in half. Place potatoes in a pot of water so they are just covered and bring to the boil. Cook for 20-30 minutes until they are soft (a knife will easily slide through)

Once cooked drain and transfer to a mixing bowl for mashing. Add the milk and margarine and mash with a masher or fork until smooth.

Whilst the potatoes are cooking preheat the oven to 220C and lightly grease a large casserole dish (about 9"x13").

Slice the onion, mince the garlic and rinse and drain the lentils.

In a large saucepan sauté the onion and garlic in the oil until soft (about 4 mins)

Add a pinch of salt and pepper. Then add the lentils, stock and thyme and stir. Bring to the boil then reduce heat and simmer until lentils are soft (35-40 mins).

In the last 15 minutes of cooking crumble in the mushrooms (or chop them and add) and stir

Optional: To thicken the mixture scoop out some of the mixture and stir in 1 tbsp Cornstarch, then return to the mixture and stir together.

Transfer to the dish and carefully top with the mashed potatoes. Smooth down with a fork and lightly season with salt and pepper.

Place on a baking sheet in the oven for 10-15 minutes, or until the potatoes start to brown on top.

Let cool slightly before serving. Will thicken upon standing longer.