Former MasterChef champ Thomasina Miers is back with a new book. She talks to Ella Walker

You will find a brachiosaurus moseying through an asparagus forest, a tiger surveying a field of Szechuan peppers, and a duck bobbing about with a load of cherry tomatoes in Thomasina Miers' new recipe collection, Home Cook. And they all look so happy.

"You can tell I was pregnant when I was making it, can't you?!" the Cheltenham-born chef and restaurateur yelps with a laugh. "Oh my God, we had so much fun!"

Miers' fifth book is all clean lines and straightforward recipes. It pops with colour and is bolstered by Mexican influences - this is, after all, the woman who co-founded popular restaurant chain, Wahaca, which is now in its 10th year of taco slinging. At its core though, Home Cook is a reflection of "how we eat at home", says Miers, 41, and how having three small children and a restaurant empire affects that.

"The food I cook now is very different to the food I cooked 20 years ago, when I had all the time in the world," she explains. "I'm a working mother, who comes home late sometimes and just has to get food out on the table, but equally, I want to feed my family good food."

The collection of 300-odd recipes, she says, is also a "guilt-free joyous approach to food", in reaction to "all this neurosis about eating and what not to eat" that currently abounds. "Healthy eating has become such a loaded, almost toxic subject," says Miers. "I grew up as a teenager full of hang-ups about food and always dieting, and it's such a bad way to live your life. Over the years, I've developed - I never say no to anything.

You have to work out what works for you, rather than letting trends and aspirational Instagram posts dictate your diet, she explains.

"Everybody's bodies are different; we all react to different ingredients in different ways, so it's nonsense to say one diet can be suitable for thousands of people, it doesn't work that way. It's about adapting your own likes and dislikes and eating the way that's right for you, and having fun with it. Basically, if you're cooking a bit from scratch at home, which you can do affordably and easily, then you're going to be eating healthily, and if you eat a few doughnuts along the way, it doesn't really matter."

Miers won MasterChef in 2005 and still appears on the series as a guest judge. Her advice for the latest crop of amateur chefs entering the MasterChef kitchen is: "Cook from your heart. The second you try and get too clever with cooking, you're found out pretty quickly. You've got to cook from your heart and soul - which is what makes MasterChef so compelling, actually, seeing people putting themselves on the line."

THAI GREEN SEA BASS WITH GALANGAL, LEMON GRASS AND COCONUT

(Serves six)

For the fish:

1 whole sea bass

A few lime leaves (optional)

A few slices of lime (optional)

100ml water, fish or vegetable stock

Lime wedges, to serve

Coconut rice, to serve

Steamed pak choi, to serve

1tbsp sesame oil, toasted

For the Thai paste:

2 star anise

Half a cinnamon stick

1tbsp black peppercorn

Thumb-sized piece of fresh galangal, peeled and sliced (available from Sainsbury's)

Thumb-sized piece of fresh ginger, peeled and sliced

4 garlic cloves, bashed to remove the skin

3 banana shallots, chopped

3 lemon grass sticks, chopped, outer layer set aside

6-8 bird's eye chillies

2tbsp fish sauce

Juice of 2-3 limes

2tbsp demerara sugar

Large bunch of coriander, leaves and stalks chopped separately

1 x 400ml can of coconut milk

Salt

METHOD

First make the Thai paste: Grind the spices and put in a food processor with the galangal, ginger, garlic, shallots, lemon grass (reserving the outer layers), fish sauce, lime juice and sugar. Blitz to a rough paste. Add the chopped coriander stalks and coconut milk to the paste with half a teaspoon of salt and blitz again until combined. Taste the paste and add more chillies (when the paste is baked, the chilli heat will reduce dramatically).

Preheat the oven to 200C/Gas mark 6. Lay out the bass in a deep roasting tin, large enough to fit it comfortably. Make a few slashes in both sides of the body and cover with enough paste inside and out so it is well coated. Stuff the inside cavity with the lime leaves, lemon grass outer layers and slices of lime if using. Mix the rest of the paste with the water or stock and pour into the tin. Bake for 25-30 minutes, or until a thin metal skewer can slide easily all the way into the thickest part of the fish.

Scatter with chopped coriander leaves and serve with lime wedges, coconut rice and some steamed pak choi laced with one tablespoon of toasted sesame oil.

UNBELIEVABLY DARK AND DELICIOUS CHOCOLATE CAKE

(Makes one large cake)

For the cake:

380g butter, plus extra for the tins

380g dark chocolate (70% cocoa solids), chopped

380g caster sugar

2 small pinches ground cinnamon

Several large pinches of salt

200g plain flour

6 eggs, beaten

For the topping:

4 Mars bars

100ml whole milk

3 tbsp golden syrup

90g dark chocolate (70% cocoa solids), chopped

500ml double cream

3 Flakes, chopped into 2cm lengths

2 packets of Rolos

1 large packet of Peanut M&Ms (optional)

Edible glitter

Preheat the oven to 190C/Gas Mark 5 and butter and line the base of two 20cm non-stick cake tins.

Melt the butter in a medium pan over a low heat; once melted, stir in the chocolate, being careful not to burn it. When the mixture becomes smooth velvet, add the sugar, cinnamon and salt. Stir until the sugar has dissolved, then slowly sift in the flour, stirring to combine. Beat the eggs into the chocolate mixture a little at a time until fully incorporated.

Pour into the prepared tins and bake for 30-40 minutes until the outside is dark and delicious looking and a skewer comes out clean. Leave to cool in the tins for 15 minutes before removing to a cooling rack.

Meanwhile chop up the Mars Bars and melt with the milk, syrup, dark chocolate and 50ml of the double cream. Whip the rest of the cream until it just holds its shape.

Sandwich the cooked cakes together with the whipped cream and pour over the Mars Bar sauce. Scatter the various chocolates and the glitter on top. Serve.

Home Cook by Thomasina Miers, photography by Tara Fisher (Faber and Faber, £25)