A 7x11-inch baking pan (aka a "brownie pan") is the perfect size for making 8 buns. They are easily found and inexpensive, so if you plan on making these buns (or brownies) often, they are definitely worth the investment. If you only have a 9x13-inch baking pan, see my tips below for how to shrink the width and bake these buns!
In a small saucepan, heat milk over medium heat until it just comes to a simmer. Set aside to cool to lukewarm (120° F. for instant yeast or 110° F. for active dry yeast). Once cooled to lukewarm, add sugar and stir in, then sprinkle yeast over top. Stir and let stand a few minutes to proof.
In a large bowl or the bowl of your stand mixer fitted with a kneading hook, combine 2 cups of the flour and the salt. Add the milk/yeast mixture and stir to combine. Start adding additional flour, a bit at a time, until dough comes together. Knead by hand or with the kneading hook until dough is smooth and moist, but not sticky. Remove dough to a greased bowl, cover with plastic wrap and allow to rise until doubled.
Grease an 7x11-inch baking pan and set aside (*see tips below if you only have a 9x13-inch pan!).
Remove dough to a lightly floured surface and divide dough in to 8 equal pieces (about 3 oz. each, if you have a scale). Shape each piece of dough in to a ball (*see tips below), then using the palm of your hand roll and stretch slightly, until it is an oblong shape, about 4 1/2-5-inches long. Place in your prepared pan, pinched side down, pushing it up against the short end of the pan slightly. Continue with the remaining pieces of dough, placing each snuggly up against the next, until all 8 are in the pan. (They should be quite snug up against each other, so that when they rise, they rise up instead of out). Spray a piece of plastic wrap, then cover pan (oiled side down) and set aside to rise until doubled.
Preheat oven to 375° F. with rack in middle of oven.
When ready to bake, remove plastic wrap and brush buns with egg, ensuring that you get some on the ends and all exposed surfaces. If using, sprinkle with poppy or sesame seeds.
Bake in pre-heated 375° F. oven for 20-25 minutes, or until golden and they sound hollow when lightly tapped. Remove from oven and let stand a few minutes. Run a knife along the edges and remove buns as one piece and place on a cooling rack to cool completely. Once cooled, using a serrated knife, cut between the rolls. To serve, place cut rolls on to baking sheet and place under the broiler to toast each side (or pop on to the BBQ and toast each side). Once toasted, make a slice lengthwise in the middle of the bun for your hot dog or other fillings.
Store any extras in an air-tight bag or freeze.
Tips: If you only have a 9x13-inch pan, fill the end 2-inches of the pan with crumpled foil balls, then make a straight edge by placing a folded piece of foil on the inside edge. This will shorten the width of the pan from 13-inches to 11-inches, so as the buns rise, they rise up instead of sideways.
To shape dough in to balls: Place the piece of dough in your palm, with the smoothest side down. Now using your other hand, start pinching opposite sides of the dough together in the centre. Turn the dough slightly and pinch again, until all the outside edges have been pinched in to the middle. Be sure to pinch well to seal, then place, pinched side down on to your work surface. The top should to taut and smooth.