Begin heating 3-4 cups canola oil on the stovetop over medium low heat. I like frying donuts in my cast iron skillet since it retains heat so well.
Mix the butter and sugar together. Add in eggs, one at a time, mixing in between additions. Add in milk and vanilla and mix to combine.
Add in dry ingredients and mix until well incorporated. Let dough rest for 10 minutes.
Flour countertop liberally. Transfer dough onto flour and sprinkle top with additional flour. Knead for 2-3 minutes, adding flour in small amounts until dough is easier to handle and less sticky. (The dough will still be somewhat sticky, but manageable. One of the tricks to delicate, soft donuts is not over mixing/ over kneading and not adding in too much flour. Between sprinkling the countertop and the flour on the dough, you'll likely use an additional 1/4 cup of flour.)
Roll dough out just a few times until it's about 1/2" thick. Use 2 different biscuit cutters to cut round donut shapes and set uncooked donuts and donut holes aside. (I made large round donuts using the smallest circle cutter and the 3rd largest, then made mini donuts by cutting a larger middle hole into the donuts I just cut.)
Once oil reaches 325-330 degrees F, begin frying 3-4 donuts at a time. Let cook 2-3 minutes on one side, then flip donuts and cook an additional 2-3 minutes. Donut holes will cook much faster, usually 3 minutes total.
Transfer cooked donuts to a plate lined with paper towels. Cool slightly.
Whisk strawberry glaze ingredients together. Dip semi-cooled donuts in, making sure to coat well. Donuts taste best when eaten immediately, while still warm and dripping with gooey glaze! Store leftovers in an airtight container. Leftover donuts will soften, but they'll still be delicious.