Melt 1 tablespoon of butter in a 10-inch cast iron skillet. Add the barley, cooking until the barley is toasted and golden brown (it should smell nutty). Remove barley from heat. Add to a small bowl and chill until ready to use (barley must be cold before it’s used in the topping or it will melt the butter and prevent the topping from cooking properly).

Make the filling while the barley cools. Add the remaining 2 tablespoons of butter, peaches, brown sugar and salt to the same skillet you used to toast the barley. Bring to medium-high heat, stirring until the butter is melted and the brown sugar is well combined with the peaches. Add the beer and bring to a strong simmer. Simmer until the liquid in the pan starts to thicken and become syrupy, about 8 minutes. Remove from heat.

Preheat the oven to 425°F.

In a food processor add the toasted and cooled barley, flour, salt and brown sugar. Process on high until the barley starts to break up, but some chunks still remain.

Add the butter and pulse until just combined. Add the topping to the top of the skillet in small handfuls until the top is mostly covered. Bake at 425°F until the top is golden brown, about 18-20 minutes. Serve warm, topped with ice cream if desired.