Stir and dissolve 1 tbsp yeast in ¾ cup milk heated to 110°F
Stir in ¾ cup bread flour until smooth.
Cover with plastic wrap and let rise in warm spot for 30 minutes.
In a bowl fitted with a mixer, food processor, or with a whisk, combine remaining ¼ cup milk (heated to 110°F), and 1 tsp yeast. Add yeast/flour mixture, egg yolks, and vvanilla extract.
Mix/pulse/whisk until smooth.
Add 1 cup bread flour, sugar, and salt. Mix for 30 seconds.
Add butter and mix until incorporated; about 30 seconds.
Switch to dough hook attachment or continue using food processor, or by hand and add ¼ cup bread flour at a time. Pulse, or knead until dough starts to come together and pulls away from the sides, repeating with flour mixture. It may take up to 2-2½ cups at this stage. I used about 2¼ cups.
Do will be soft, and moist but sticky. It shouldn't be so sticky that it cannot be rolled out.
Lightly grease a large bowl with butter.
Add dough to bowl and cover with plastic wrap or kitchen towel and let rise in a warm spot for 30 minutes.
Gently press down to let the air out (degas).
Cover again and refrigerate for 1 hour or up to 12 hours.
Line two baking sheets with parchment paper and lightly flour; set aside.
Lightly flour a clean, flat work surface.
Roll dough into ball. Lightly flour the top of the dough and the rolling pin.
Roll dough to ½-inch thickness.
Using a donut cutter, cut 3-inch circles with 1-inch (for donut holes) circles in the middle and place donuts 1-inch apart on prepared baking sheets.
Allow dough to proof and rise in warm spot 30-40 minutes or until double in size.TIP: Donuts are ready when lightly touched with a fingertip, the dough springs back slowly. If dough springs back immediately, it needs more time. If dough doesn't spring back, it will need to be rerolled and proofed for 30 minutes.
Preheat air fryer to 350°F. Lighty grease basket and tops of donuts with cooking spray.
Bake whole donuts for 3-4 minutes or until lightly golden brown. Bake donut holes separately for 2-3 minutes.
Move to cooling rack. Make glaze by whisking ingredients together until incorporated and smooth.