French Lavender (Lavender stoechas, zone 8) grows fast by seed in a sunny window, with true flowers vs. narrow sprigs.
All Lavender is edible but most of them don't taste that great. Grow English Lavender (Lavandula angustifolia) if you plan to cook with it.
1.25 cups butter
1 cup sugar
3 cups flour
4 tablespoons fresh lavender flowers, crushed
Cream together butter, sugar and eggs. Mix in the flour and lavender flowers. Spoon onto a cookie sheet. Bake about 15 minutes @ 350 degrees F. (You might as well double the batch right now because you know in your heart that you want to...)