- Mix all the crumble ingredients EXCEPT for the butter and lemon juice in a large bowl. Then, add the butter and lemon juice and rub both into the flour with your fingertips. Do this until there is no more dry flour and you have a mix of both coarse and small crumbs. Cover and refrigerate.
- Make sure you have your stock and milk ready to use at this point. Melt the butter for the filling in a large pot over medium heat. Using a whisk (use silicone coated if you have a pot with a delicate surface), stir in the flour. Whisking constantly, cook the flour for one minute. Add the minced garlic and continue whisking for another 30 seconds. Pour the stock into the pot, whisking vigorously to remove any lumps of flour. Once it’s smooth, whisk in the milk, mustard, salt, nutmeg and pepper.
- Preheat the oven to 390°F. Bring the sauce to a boil, add the potatoes and leeks and reduce to a simmer. Cook for 5 minutes. Stir in the peas, ham and chives.
- Pour the filling into a 7×11 rectangular baking dish. Evenly top with the crumble topping. Bake for 30 minutes or until the filling is bubbly and the topping golden brown.
- Serve immediately topped with chopped chives, parsley and sliced scallions, if you like.
This dish can be made ahead of time. Follow the steps 1-3, omit preheating the oven. Assemble the crumble in a baking dish, then cover and refrigerate for up to 24 hours. Allow 10-15 extra minutes for baking, as the dish will be cold out of the fridge.
You can also choose to freeze this dish for up to three months. Wrap the baking dish very well to avoid freezer burn. Clearly label with the recipe name, date and instructions for cooking. Defrost the dish in the fridge overnight and add 10-15 minutes to the baking time stated in the recipe.
The calories are per serving.