Preheat oven to 400 F
In a medium or large saucepan, combine jalapenos, onion, garlic, and butter. Sautee for a few minutes, until onion and peppers soften up a little.
Add rice flour, whisk until well distributed and free of clumps.
Add beer, whisking well until smooth. Add heavy cream, continuing to whisk, until smooth. Bring to a boil.
As mixture starts to boil, add shredded jack cheese, continue stirring until melted and smooth. Remove from heat, season with salt and pepper to taste.
Peel potatoes if you like – we don’t bother, we like the skins! – and slice VERY thinly. I like to use a mandolin, as it saves time.
Spray a 9 x 13 baking dish, and layer about a third of the potatoes in there. Pour a third of the sauce over it, tilting the pan to let it seep through the layers.
Layer another third of the potatoes, pouring another third of the sauce over it. Repeat one more time, using up the remaining potatoes and sauce. Cover with foil.
Bake for 1 hour. Remove foil, return to oven for another 20 minutes. Remove from oven, scatter cheddar cheese evenly over the top, and return to the pven for another 10 minutes, or until nicely browned.