The blue-sky days of early spring are currently sandwiched between chilly mornings and even colder evenings. As dinner time approaches, my idea of tossing together a light spring salad all too often turns into the need for a baked potato the size of a rock, butter running down its crisp, salt-crusted skin.

Over the years, sweet potatoes, their orange flesh glowing like a beacon, have begun to replace the trusty Maris Pipers as baked potato of choice. Curvaceous and thin-skinned, their soft interior cooks to a buttery fluff that is infinitely sweeter than a Maris Piper or King Edward. You either like the sugar hit or you don’t. You can tame the sweetness with chilli and coriander or lime. Cheese works if it is white, sharp and salty, like feta or Ticklemore. Golden, fat-rich varieties much less so.

Earlier in the week I made a green butter for a baked sweet potato with spinach leaves and a seasoning of red chillies, salt and lime. This verdant butter would work with a floury white tattie, too, though I would swap the seasonings for a smidgeon of grated nutmeg and a handful of sautéed button mushrooms instead.

I also made mash this week, a reassuringly soft and velvety batch with a stirring of crème fraîche and plenty of black pepper. We ate it with leeks that we cooked on the griddle until their outside leaves sent up smoke signals. Desperate as I am for full-on spring cooking, these few last weeks of cold evenings do have their perks.

Sweet potato, spinach butter

Sweet potatoes sometimes split their thin skins as they bake, the sugary flesh leaking out and cooking to a crisp on the oven floor. I find lining the baking sheet with foil saves tiresome washing up.

Serves 4

sweet potatoes 4

spinach leaves 100g

butter 125g, at cool room temperature

spring onions 3

coriander leaves 10g

red chillies 1, large, mild

lime 1

Set the oven at 200C/gas mark 6. Bake the sweet potatoes on a baking sheet for about 45-60 minutes, depending on their size, until they are tender. Wash the spinach leaves, discarding any very thick stalks. Pile the still-wet spinach leaves into a deep pan, add 100ml of water, then place over a moderate heat and cover tightly with a lid. Bring the water to the boil, shaking the pan from time to time, then lift the lid and turn the spinach over, cover and steam for a minute more.

When the leaves are bright and relaxed, drain in a colander, then squeeze out as much water as possible. (I find rinsing the spinach briefly under cold water helps cool it enough to handle.) Chop the leaves roughly and set aside in a small bowl.

Cream the butter until light and fluffy. Slice the spring onions into wafer thin rounds and add to the butter. Coarsely chop the coriander and the chilli, then add to the butter. Squeeze in the juice of the lime, add the chopped spinach and a generous pinch of salt, then combine everything together. You can keep this in the fridge until you need it.

When the potatoes are soft and fluffy inside, split them open and spoon in the spinach butter, letting it melt into the hot potato.

Griddled leeks, crème fraîche mash

Juicy and sweet with a buttery exterior: griddled leeks and crème fraîche mash. Photograph: jonathan Lovekin/The Observer

By steaming the leeks prior to grilling you get the best of both worlds, a leek that is juicy and sweet with a deliciously toasted, buttery exterior.

Serves 2-3

For the mashed potato:

floury potatoes 1kg

butter 30g

crème fraîche 100g

For the leeks:

leeks 4, medium

butter 35g

For the butter:

frozen peas 100g

pumpkin seeds 1 tbsp

butter 40g

sunflower seeds 1 tbsp

mint leaves to serve

Peel the potatoes, cut them into large “roast potato-size” chunks, then boil them in salted water for 15-20 minutes until tender. Steam them if you prefer.

Trim the leeks, discarding the root end and any dark green leaves. The trimmings are a worthy addition to the stock pot. Cut each leek in half then wash thoroughly in cold running water, letting the water penetrate right down in between the layers as much as possible. If they are very muddy, I suggest leaving them to soak in cold water for a while.

Bring 200ml of water to the boil in a large, deepish pan, add the leeks and the butter and let them cook for about 9-10 minutes, until they are tender to the point of a knife. Lift out the leeks and drain on kitchen paper.

For the butter, put the peas and pumpkin seeds in a food processor and pulse briefly to coarse crumbs.

Warm a griddle pan, then lower the leeks on to the hot griddle. They will brown quickly because of the butter with which they were cooked. Turn them as necessary until evenly toasted, then remove from the heat.

Drain the potatoes, add the butter, and mash them thoroughly with a potato masher or fork. Stir in the crème fraîche and a light grinding of black pepper, then beat until fluffy with a wooden spoon.

Melt the 40g piece of butter in a shallow pan, add the peas, pumpkin seeds and the sunflower seeds and cover cook over a moderate heat for 3-4 minutes.

Pile the potato on a warm serving dish, place the griddled leeks on top then spoon over the peas, seeds and their butter, scatter with mint leaves and serve.

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