In a small saucepan, heat the milk until lukewarm (about 95°F). Remove from the heat and whisk in the yeast until it dissolves. Add the oil and butter—the butter may begin to melt, but it’s OK if it doesn’t melt completely—and then whisk in the sugar. Let rest until the yeast just begins to float to the surface, about 5 minutes.

In a stand mixer fitted with the paddle attachment (or in a large bowl), combine the flour, salt, and egg. Add the yeast mixture and mix on low speed (or with a large spoon) until a coarse ball of dough forms, about 1 minute. Let rest for 5 minutes.

Replace the paddle attachment with the dough hook and mix on medium-low speed (or knead by hand on a lightly oiled work surface) until the dough feels soft, supple, and pliable, about 3 minutes; it should feel tacky to the touch, but not sticky, and pull away from your finger when poked instead of sticking to it. If the dough is too sticky, add 1 Tbs. flour at a time, kneading to incorporate. If it’s stiff, knead in 1 Tbs. of milk at a time.

Rub a little vegetable oil on a work surface to create an 8-inch circle and put the dough on this spot. Stretch and fold the dough over itself from all four sides to the center, crimping it where the folded ends meet, to form it into a tight, round ball.

Put the dough seam side down in a lightly oiled bowl that’s twice the size of the dough. Tightly cover with plastic wrap. Let sit at room temperature until doubled in size, about 90 minutes.

Line two 13x18-inch rimmed baking sheets with parchment or nonstick baking liners and lightly mist them with vegetable oil spray.

Using a bench knife, divide the dough into eighteen pieces (about 2-1/4 oz. each).

With your hands, roll one piece into a 12-inch-long rope. If the dough starts to stick, mist your work surface lightly with vegetable oil spray or wipe it with a damp towel. Don’t use flour.

Wrap the dough around your fingers into a loose knot; there should be about 2 inches of dough free at each end. Wrap the left end of the dough up and over the loop. Wrap the right end down and under the loop. Lightly squeeze the two ends of dough together in the center to secure them.

Gently squeeze the whole piece of dough into a nice rounded shape. Put the roll, pretty side up, on a baking sheet. Repeat with the remaining dough. Mist the top of the rolls with vegetable oil spray and cover loosely with plastic wrap.

Let the rolls sit at room temperature or refrigerated until they just begin to swell, 30 minutes to 1 hour for room-temperature dough, 1 to 1-1/2 hours for refrigerated dough.

Position racks in the upper and lower thirds of the oven. If using a convection oven, heat it to 375°F; if using a conventional oven, heat it to 400°F.

Thoroughly whisk the egg with 1 Tbs. water and brush all over each roll. Sprinkle poppy or sesame seeds (if using) on the rolls.

While the oven heats, let the rolls continue to rise at room temperature, 20 to 40 minutes. They should be 1-1/2 to 2 times their original size before they go in the oven. (Once in the oven, they will rise about 20 percent more.)

Put the baking sheets in the oven and bake for 6 minutes. Rotate the sheets 180°F and swap their placement on the racks. Continue baking until the rolls turn rich golden-brown on top and develop some browning underneath, another 6 to 8 minutes. Let the rolls cool on the sheets or on a cooling rack for 15 minutes before serving.