I'm not sure if this is the right way to say this - you might have a better idea.

This is how the story begins - Is mar seo a thosaíonn an scéal sin -
In a dark dark town, - I mbaile dubh dorcha,
There was a dark dark street, - Bhí sráid dubh dorcha,
And in that dark dark street, - Is sa tsráid dhubh dhorcha sin,
There was a dark dark house, - Bhí teach dubh dorcha,
And in that dark dark house, - Is sa teach dubh dorcha sin,
There were some dark dark stairs, - Bhi roinnte staighre dubh dorcha,
And down those dark dark stairs, - Is thíos an staighre dubh dorcha sin,
There was a dark dark cellar, - Bhí siléar dubh dorcha,
And in that dark dark cellar, - Is sa shiléar dhubh dhorcha sin,
Some skeletons lived, - D'áitrigh roinnte cnámharlacha,
There was a big sketelon, - Bhí cnámharlach mór amháin,
And a little skeleton, - Is cnámharlach beag amháin,
And a dog skeleton, woof! - Is cnámharlach madra, bhuaf!

Could I say dorcha, dorcha ?

I'd say "an scéal seo" since you're telling it



sráid dhubh dhorcha (except if you meant "a street was dark dark" ?)



staighre is like "escalier" in French, so I doubt you can put "roinnt" before it (would be "quelques escalieR"...)



sa siléar dubh dorcha (or in Ulster and maybe elsewhere: sa tsiléar dhubh dhorcha)



roinnt

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

That's how the story is told - (in French it's - dans une sombre, sombre maison etc) and I also remember, though for moment I can't find it, that there was a Irish-speaking organisation in Ulster who produced a series of children's story books with CDs where the storyteller used the same technique - a small, small man in a small small house srl - it sounded something like bweedach, bweedach - you could listen to it on-line.
So - staighre gan roinnt. Is there anything else?
I'm reading it from a picture book (in English it's called Funnybones and in French it's les Bizardos)

baoideach
(you'll find the variant "bídeach" in dictionaries, but in Ulster the b is broad)

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

ça y est j'ai trouvé! - Seanchas Rann na Feirste - Mo Ghabhar Beag Baoideach Baoideach le John Ghráinne Ó Duibheannaigh
http://www.rannafeirste.com/sampla.html
An t-údar is taighdeoir ar na teangacha Ceilteacha é an t-údar ach tá suim ar leith aige i nGaeilge Thír Chonaill. Is féidir tuilleadh eolas faoi a fháil ach gabháil chuig súiomh Scoill an Léinn Cheilteach.
(The link still won't work)

Agus is truaigh liom nár cheannaigh mé 'n leabhar sin go díreach i ndiaidh a foilsithe, nó tá sé rómhall anois :-(

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

bump

I'd say Is mar seo a thosaíonn an scéal - without seo or sin since it is just "the story" not "this story" or "that story". (Does the French have ce/cette/cet or le/la/l'? cet histoire or l'histoire? - either way I think an scéal alone would still carry the meaning.)

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

Funnybones is English - written by Allan Ahlberg and illustrated by his wife Janet, who sadly is no longer with us. It's very well-known by children especially for its accumulative rhyme - a dark, dark cellar etc, which leads me to the question - can you use this narrative technique of two adjectives one after the other in Irish? The reference that I gave above is in fact an example of this.

Mo Ghabhar Beag Baoideach Baoideach (le John Ó Duibheannaigh)

D'éirigh mé ar maidin go baoideach baoideach
Agus chuir mé síos tinidh bheag bhaoideach bhaoideach
Scuab mé an t-urlár beag baoideach baoideach
Agus fuair mé sé pingne beag baoideach baoideach

D'imigh mé chun an aonaigh go baoideach baoideach
Agus cheannaigh mé gabhar beag baoideach baoideach
Ag pilleadh chun an bhaile damh baoideach baoideach,
srl srl

It has been translated into French (Bizardos) and thankfully, in this instance, they've kept the same rhythm. Unfortunately there's another well-known children's book that uses the same idea (A Dark, Dark Tale by Ruth Brown) which has been translated as 'Une Histoire sombre, très sombre' which entirely breaks the rhythm of the original. This technique is typical in oral literature in many languages and is a way of inviting the listeners to join in and become part of the story, as well as being a technique that helps the storyteller remember the story - but apparently you don't often find this in the Irish tradition and I don't know why.
I'll be trying to translate another version later on.

http://www.youtube.com/watch?v=RZYsUOZmRwM - Funnybones Intro

I think Irish usually prefers an alliterative pair over straight repetition:

beag bídeach "tiny-little"
dubh dorcha "pitch-dark"
mór millteach "great big"

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).