Preheat oven to high grill. Bring a large pot of salted hot tap water to the boil. Set aside a large baking dish.
Cook pasta
Add 250 g penne pasta to the pot of boiling water and cook on high heat for 8 minutes, stirring occasionally. Meanwhile, cut 1 broccoli into florets. When the pasta has been cooking for 8 minutes add the broccoli and 1 cup frozen peas and cook for a further 4-5 minutes until the pasta is cooked through and the broccoli is tender. Drain well and add to the baking dish.
Start sauce
Cut 1 leek in half lengthwise and thinly slice. Wash and grate 1 parsnip. Heat 1 tbsp olive oil in a large frypan on high heat. Add the leek, parsnip and a pinch of salt to the pan and cook for 4-5 minutes, until tender and starting to colour. Add 450 g pork mince and cook for about 4 minutes, breaking up the lumps with a wooden spoon as you go.
Finish sauce
Add 1 ½ cups chicken stock to the frypan and bring to a simmer. Once simmering, remove the pan from heat. Stir through ½ cup sour cream and season to taste with salt and pepper.
Make crumb
In a medium bowl combine 2 tsp dried thyme, 1 cup panko breadcrumbs, a pinch of salt and 1 tbsp olive oil.
To finish
Pour sauce over the pasta in the baking dish and toss to combine. Sprinkle over the crumb. Grill on the upper oven rack for 3-5 minutes, until golden brown. Pick the leaves and roughly chop 1 bunch mint leaves.
To serve
Divide creamy pork and leek pasta bake with herbed crumb between plates. Garnish with the mint.