Place the flour, kosher salt and baking powder in a food processor fitted with the steel blade and pulse to mix. Add the butter and pulse until the mixture resembles coarse meal. Add the Cheddar, jalapeno and chipotle chili powder and pulse again. With the food processor running, add the ice water all at once. Continue pulsing until the mixture begins to form a ball. Dump the dough onto a floured board and roll it into a 14-inch log. Wrap in plastic, and refrigerate for at least 1 hour.
When ready to bake, preheat the oven to 400 degrees F. Line a sheet pan with parchment paper.
Cut the dough in 3/8-inch-thick slices. Place the crackers on the prepared sheet pan, brush with the egg wash and sprinkle with the fleur de sel. Bake for 12 to 15 minutes, until golden brown. Serve slightly warm or at room temperature.