Indian-inspired potato and mustard seed curry

I had a craving for a potato curry that was flavoured with mustard seed and coconut milk, and cooked in the slow cooker. I found this recipe and modified it to my taste and cooking method.

Here's what I ended up making. It was delicious! Very easy with minimal preparation time, and extremely cheap to cook.

Ingredients
1.5kg potatoes, cleaned and diced into large chunks
1 tbs vegetable oil
2 tbs black mustard seeds
3 garlic cloves, crushed
2 tbs crushed ginger
red chilli, to taste (I used 1.5 very hot small chillies)
2 tsp turmeric
12 curry leaves
8 small tomatoes, cut into wedges
400mL coconut milk

Heat vegetable oil in a frypan over medium heat.
Add the mustard seeds and fry until they start to pop.
Add the garlic, ginger, chilli and turmeric and fry while stirring for 1 minute, then remove from the heat.
In a large slow cooker (mine is 5L), add the coconut milk, tomatoes and curry leaves.
Add the mustard seed mixture and stir well.
Add the potatoes, and enough water to only just cover the potatoes, and mix.
Leave to cook, stirring occasionally, until potatoes are done. This will vary depending on the type of potatoes, how small they were diced and the cooking ability of your slow cooker, but it took me about 3 hours on high.
If the sauce needs thickening, combine 1 tbs cornflour with 1/4 cup cold water and add to the curry.
Garnish with coriander if you have some (sadly I didn't!).

I served this with home-made roti. They turned out ok but weren't brilliant, so I will work on the recipe, and post once I'm happy with it!