Mix active dry yeast, a tablespoon of sugar and warm milk in a medium bowl. Leave it to bloom for 10 minutes. It will get foamy at the top. Whisk in egg and butter, then transfer into a bowl of a stand mixer. Attach a dough hook to your mixer.
Whisk together flour, diastatic malt powder and sugar in a large bowl. Pour half of the mixture into your stand mixer bowl and mix on the lowest speed for 30 seconds, then increase to the next speed setting and mix for 1 minute. Decrease the mixing speed to the lowest setting again and add the remaining flour mixture. Knead in the mixer between the lowest and medium-low setting (depending on your stand mixer instructions for mixing bread dough) until the dough doesn't stick to the sides of the bowl and the bowl is basically clean and free of loose flour or sticky dough. How to tell if the dough is ready: It will quickly bounce back if lightly pressed with a finger. Detach the bowl from your stand mixer and give the dough inside a few turns with your clean hands, pulling the sides into the center, creating a ball.
Lift the dough ball and spread the vegetable oil on the bottom and sides of the mixing bowl with your fingertips. Place the dough back inside and turn it in the bowl to coat it with oil. Cover the bowl with plastic wrap or clean kitchen towel and leave in a warm, draft-free place (an oven that's not turned on would work). Let it rise for 1 hour. The dough will double in size/volume.
Preheat the oven to 350°F, if baking the buns same day.
Divide it into 4 pieces and shape each portion into a ball, tucking the sides into the center until taut.
Work each ball by flattening it with your fingertips into an 8" x 6" rectangle. Roll the it tightly along its length (i.e. longer side) and pinch the edges to the roll to seal, and pinch both sides of the roll, leaving you with a compact and sealed cylinder.
Slice it crosswise into six 1- to 1.5-inch discs.
Dip cut sides into the plate of breadcrumbs and pat to remove excess crumbs.
Place each bun cut side down on the lined baking sheet, arranging the buns into 6 x 4. Loosely cover with plastic wrap or a clean kitchen towel let them rise for 1 hour. [Overnight 2nd rise:If you make this in the evening, you can leave it in the refrigerator overnight for a slow rise, then bake them in the morning. A slow rise gives the dough more time to develop its flavor.]
Bake in the preheated oven for 30 minutes, or until the tops of the buns turn golden brown. Remove from the oven and let it rest in the baking pan propped on a cooling rack for 15 minutes. Serve warm or transfer and cool completely on the wire rack before storing in airtight containers or resealable bags.