The curly is better for garnishing, it keeps longer when refrigerated. I use the flat variety in my garden. Host plant to the Black Swallowtail caterpillar. You could also start with plants. Boil water in microwave, then add seeds.
Parsley seeds have a chemical that prevents germination.
After changing water, soak another 24 hours. Germinate in damp paper towels and zip lock baggies. Transplant seedlings in the garden one week prior to your last frost date, being careful not to injure the taproot. This could cause the plant to flower and set seed prematurely. Must be well drained, or the roots will rot if wet.