Croissants don't require tremendous skill or equipment, but they do require time and several specific steps. Don't let words like preferment or laminate hold you up. These are 150% worth the effort!
Heat the milk until it is just warmed through, about 80-90 degrees. I tend to do this in the measuring glass in the microwave in short spurts so the milk doesn't get too hot. Pour the milk into the bowl of your mixer and stir in the yeast until dissolved. Add the flour and stir the mixture with a wooden spoon until a sticky dough forms. Cover the bowl with a cloth or plastic and let the mixture rise until it has almost doubled in volume. This will take 2-3 hours at room temperature or overnight in the refrigerator.
Add the yeast for the dough to the preferment mixture and mix together on low speed with the dough hook until evenly combined. When the mixture has come together, increase the speed to medium and mix for a couple of minutes. With the mixer running, slowly add in half of the milk a little at a time and mix until well combined. If you add in the milk too quickly it will take a bit of time to loosen the dough up. If you are patient you can loosen the dough with just a little milk added bit by bit. Either way, it will come together. Reduce the speed to low and add the remaining milk, flour, sugar, salt and melted butter. Mix until the dough comes together, about 3 minutes. Turn off the mixer and let the dough rest for 15-20 minutes, loosely covered.
Turn the mixer back on low speed and mix the dough until it is smooth and elastic, no more than 4 minutes. If the dough seems very firm, add in more milk, 1 tablespoon at a time. I added a few tablespoons. Make sure to not overmix the dough as over-mixed dough will result in tough croissants--definitely not what you want at the end of this adventure. Cover the bowl with a cloth or plastic wrap and let it rise until the volume increases by half, about 1 1/2-2 hours.
Lightly flour a work surface and transfer the dough to the surface. Gently press the dough into a rectangle 2'' thick. Wrap the rectangle in plastic wrap and place it in the refrigerator to chill for 4-6 hours. It will continue to proof in the fridge so do not be surprised to return to dough that is stretching the bounds of the wrap.
Lightly flour a work surface and place the refrigerated dough on top. Again, roll the dough to a 28 inch by 12 inch rectangle and fold it into thirds. Place the rectangle back on the quarter sheet pan and wrap tightly with plastic. Place the pan in the freezer for at least one hour.