I hope I'm not a smug person, but I will admit that I did feel very smug the other day as I strolled along a boiling hot Soho street eating ice cream from Gelupo, the gelateria recently opened by the team behind the truly fantastic trattoria, Bocca di Lupo. Turning a corner, I walked straight into a woman with a Magnum in her hand. Ha! Bad choice, lady. I know a Magnum only costs £1.10 or thereabouts, but they are also sickly sweet, unctuous and heavy on the stomach (not to mention the thighs); far better, I think, to spend your hard-earned money on one cone from Gelupo than three from Wall's (at Gelupo it's £3.50 for two scoops). The woman and I looked at one another for half a second. I've no idea what she was thinking but, in my mind, we were in the ice-cream equivalent of the scene in Raiders of the Lost Ark in which Indiana Jones deals with the scimitar-wielding baddie by simply getting out his gun. Put a three-scoop combo of home-made chestnut, pistachio and ricotta-honey-coffee up against a stick of corn oil, whey solids and seaweed-based stabilisers, and… no contest. The bell should ring before the fight even begins.

I'm in the grip of an ice-cream obsession at the moment. There are several reasons for this. First, it has been very hot. Second, ice cream is one of the few puddings T seems genuinely to like. Third, I have finally bought myself a machine, which has opened up a whole world of new possibilities for me, among them one that goes by the name of plum and Earl Grey tea ice cream (for the recipe, see the very good book Lola's Ice Creams & Sundaes by Morfudd Richards). More exotically, on a visit to the collection of cookery books at the Guildhall Library in the City of London, a wonderful foodie librarian called Peter Ross made the mistake of introducing me to Mrs Agnes B Marshall, aka the Victorian queen of ice cream. In spite of my deep love for old cookbooks, I'd never come across this Agnes B before, probably because The Book Of Ices is not exactly the kind of thing one stumbles on in the mouldy secondhand shops that I frequent. It's super-rare: when I tried to buy it on Abe, only modern facsimiles were available, and I prefer tooled leather when I can get it.

Agnes B Marshall (the "B" is for Bertha) was born in 1855, and had a successful career as a cookery teacher at her school in Welbeck Street where the curriculum included lessons in curry-making from an English colonel who had served in India. But it was ice cream that was her passion. She is credited with being one of the first cookery writers to mention "cornets… made with almonds and baked in the oven", and patented a design for a wooden machine which she claimed could freeze a pint of ice cream in five minutes (it has since been tested by the food historian, Ivan Day, and it turns out she was being entirely truthful). She used this machine to make the most spectacular moulded ices, among them her extraordinary Rosseline Bombe, a snowy confection flavoured with rosewater, maraschino and preserved cherries. I saw an engraving of this bombe – it was wearing spun sugar, in the manner of a mourning veil – and I fell in love. What a strange, beautiful thing: that in a world without refrigerators she was turning out stonking great banquets – towers of fruit, fat bunches of "asparagus", serene-looking swans – made entirely from ice cream and sorbet.

Meanwhile, my own adventures in ice cream continue at a more domestic pace. I have made a vat of coffee ice cream, but it tastes – as both coffee and pistachio ice creams often do – rather strongly of almond oil. How to remedy this, I wonder? And then there's my beloved brown bread ice cream. I wrote of my passion for this old English pudding a couple of months ago, pleading for its return to restaurant menus everywhere. Afterwards, a few of you wrote to say that it is available at branches of Bettys tea rooms across Yorkshire. This is good news, but I am not in Yorkshire nearly as often as I should be. So I will just have to do it myself. The best recipe – the only recipe I can find – is in Jane Grigson's English Food. It is extremely simple – bread, sugar, eggs, cream – and extremely good. The only downside – how absolutely typical! – is that, as Grigson quietly notes, this is an ice cream that needs "no attention" while freezing. My gleaming new bit of kitchen kit will just have to sit this one out. rachel.cooke@observer.co.uk