In a spice or coffee grinder, grind chia seeds until finely ground; measure out ½ cup. Then grind sunflower seeds until finely ground; measure out 1 ½ cups. (A high-powered blender or food processor would also work here.) Pour seed meals into a large bowl.
Add Parmesan, fresh rosemary, garlic powder, and baking powder, then mix.
Add egg and melted butter, mixing until dough comes together.
Turn dough out onto large sheet of parchment paper; form into a rectangle. Top with another large sheet of parchment paper. With a rolling pin, roll out to roughly ⅛" thick. Remove top sheet of parchment.
Using a pizza cutter, sharp knife, or bench scraper, cut dough into 2" squares. Transfer dough and parchment paper to baking sheet. Sprinkle with as much or as little kosher salt as you like.
Bake 40–45 minutes or until edges are golden brown and crackers are firm to the touch. Remove from oven and let cool completely, then separate crackers.