In Canadian French, "tarte au sucre" means a real sugar pie: flaky pie crust with a sweet filling, along the lines of shoofly pie. In France, though, it's the name of a yeasted cake with sweet topping. To make one, first you make a brioche dough and pat it into a buttered springform pan. Then you spread the top with soft butter, and sprinkle sugar over that. In the oven, the sugar and butter melt into a crunchy sweet crust over a tender but substantial base.
Despite the name, it's not excessively sweet, and it makes an excellent breakfast or teatime snack. After the first day, I like to cut a wedge, then warm it in a toaster oven. (Keep an eye on it lest you burn the topping.) This magically restores it to soft freshness and adds a little bonus toasty flavor. With toasting, the slices we ate on Thursday were as good as the ones we'd had on Sunday.
Of course yeast doughs take a little extra planning, but this one is pretty straightforward, with its long cool overnight rise. I plan it like so: Start the dough on Friday or Saturday evening, then pop it into the fridge. The next morning, take it out first thing and go about your business showering, having breakfast, and so on while it comes to room temperature, or take it out after breakfast and go run a few errands. Then you can bake it up around lunchtime and have your first taste as an afternoon snack. Instructions below assume a stand mixer.
TARTE AU SUCRE
1/3 c. of milk
2 T. white sugar
1 t. yeast (SAF instant preferred)
Optional but gorgeous: a fat pinch of saffron
1 1/2 c. flour
2 large eggs
3/4 t. salt
6 T butter AT ROOM TEMPERATURE
And for the topping, later:
3 T butter, very soft
1/3 - 1/2 c. brown sugar (I included a little pearl sugar too, just for fun.)
First, scald the milk. That is, bring it nearly to a boil over a very low flame, and then remove from the heat. You want steam to rise from the surface and tiny bubbles to just appear around the edges. This denatures proteins that interfere with gluten structure (at least, I think that's what the issue is). Add your pinch of saffron, if using. Let cool to bath temperature or a bit cooler. It won't take too long. If you're using non-instant yeast, stir it into the milk once it's cooled.
In the bowl of a stand mixer, first mix and then knead the flour, eggs, yeast, sugar, salt, and milk. Knead the dough for ten minutes, or until very smooth and elastic. Now add the soft but not melting butter one tablespoon at a time, running the mixer after each addition until the butter is fully incorporated.
Transfer the dough, which will be quite soft, to an oiled bowl, cover tightly, and refrigerate overnight.
The next day, let the dough warm to room temperature, still in its bowl, for about two hours. In the meantime, you should make sure that you have the topping ingredients ready. To remind you, that's:
3 T butter, very soft
1/3 - 1/2 c. brown sugar
Tip out onto a well floured surface and pat into a 9" round. Transfer into a well buttered 9" pan. Springform is extra nice but not required. Preheat the oven to 400 degrees F. and let the dough rest for 15 minutes. Spread with the soft soft butter -- if it's not soft enough to spread easily, work it with your spreading tool until it is. Sprinkle the sugar thickly over top, and let rest for 15 minutes more.
Bake for 20-30 minutes. Let cool in pan for about 10 minutes, but not much longer. You want to turn it out (or spring it) before the sugar hardens. Let cool the rest of the way right side up on a rack.