I just made the dish the way I would make a "normal" casserole. Browned the lamb (which had been marinated in garlic, thyme, bay and a little vegetable oil); softened the onions, added peeled carrots and turnips; topped-up the dish with stock and a good glug of red wine, brought it to the boil and left it to simmer for about two hours. About half an hour before serving-time I added a handful of frozen peas for some extra colour.
I actually added the turnips in two batches, because (being bought ones) I was unsure of their cooking characteristics. I put some in right at the start, cut into large pieces, and then I added some later, cut into smaller pieces so that they would cook quicker. Both batches performed well - the texture of the larger pieces was particularly appealing - soft, almost gelatinous, but the turnips didn't disintegrate as I feared they might.
I served my dish with an accompaniment of Cavolo Nero from the garden. This dish was also one that I made up more or less on the spur of the moment, but inspired by something that Sara from Hillwards had said in a comment on my post called Spotlight on Cavolo Nero.
I removed the tough central veins from about a dozen large Cavolo Nero leaves, and tore the remaining soft parts into smallish pieces. I fried some smoked streaky bacon in olive oil until crispy, turned off the heat and added some finely-chopped garlic (also home-grown). The residual heat in the pan was sufficient to cook the garlic wthout burning it - which makes it bitter. Later (a few minutes before serving) I re-heated the bacon, added a splash of red wine vinegar (to give the dish a bit of a lift) and tipped in the Cavolo Nero. The kale cooks very quickly, and what looked like a monstrous pile of leaves soon collapsed into a manageable panful. It only took a couple of minutes to cook:
The finished dish was served alongside the Navarin, with the addition of some boiled new potatoes.
In the last photo above you can see one large piece of turnip (centre), which is a lot darker than the smaller whiter pieces on either side of it. The big piece has absorbed more of the lovely lamb gravy during its longer cooking time. It's nice to have different textures in a dish like this, even if it does entail adding ingredients at different times.
This meal is very typical of the type of food I like to cook. Easy, but very satisfying, and making maximum use of good ingredients that are not excessively messed about with.