Spinach leaves can be crafted (shapeless) into seeds and planted in tilled dirt
Spinach plants can be right-clicked to harvest and it leaves the plant to grow again.
Stock = Pot + Spinach
Steamed Spinach = Pot + Spinach + Water
Spinach Pie = Bakeware + Dough + Spinach + Cheese + Toast
Beef Wellington = Raw Beef or Firm Tofu + Dough + Any Mushroom + Spinach