In a large bowl, whisk together the flour, salt, and baking powder until evenly combined. This step only takes a minute but makes sure your leavening and seasoning are spread throughout the dough instead of clumped in one spot.
Add your cold, cubed butter to the flour mixture and use a pastry blender or your fingers to work it in until it resembles coarse sand. Stir in the freshly shredded cheddar so it's evenly distributed throughout the crumbly mixture.
In a small bowl, whisk together the egg and heavy cream until smooth. Pour this mixture into the flour and cheese mixture, stirring just until a shaggy dough starts to form.
Use your hands to gently knead the dough a couple of times right in the bowl, just enough for it to form a cohesive ball. Avoid overworking it here, since too much handling can make the crackers turn out tough instead of tender.
Shape the dough into a flat disk, wrap it tightly in plastic wrap, and refrigerate it for about an hour. This resting time firms the butter back up and makes the dough much easier to roll out thin.
On a lightly floured surface, roll the chilled dough out into a thin, even rectangle, about ⅛-inch thick. Use a pizza cutter or small round cutter to slice the dough into your desired cracker shapes.
Transfer the crackers to your lined baking sheets, prick each one a few times with a fork, and sprinkle with flaky salt. Bake at 400°F for 10 to 12 minutes, until the edges turn lightly golden and crisp.