Preheat the oven to 400 degrees f. Bring a large pot of very salty water to a boil.
Carefully remove the outer leaves of the cauliflower. With a sharp paring knife, remove as much of the stem as you can while keeping the whole cauliflower intact.
Carefully lower the whole cauliflower into the boiling water and boil for exactly 6 minutes, flipping over in the water halfway through. Remove and let drain and cool.
In the bowl of a food processor combine cream cheese, jack cheese, eggs, minced garlic, salt and pepper. Pulse a few times to combine.
Add artichoke hearts and baby spinach leaves and pulse until spinach leaves look like roughly chopped herbs. The filling will be loose.
Fill a large piping bag or resealable disposable/compostable bag with the filling and cut a small hole in the tip or corner.
Carefully turn the cauliflower stem side up and pipe the filling into the nooks and crannies of the cauliflower. You may need to use your fingers to gently poke it down. It may leak out of the top a little bit, that is ok. Keep going.
When the cauliflower is filled, carefully flip it over into a baking dish. Drizzle the top all over with a tablespoon of olive oil.
In a small bowl, stir together panko breadcrumbs, parmesan cheese and remaining olive oil.
Press breadcrumb mixture all over the head of the cauliflower. If the topping falls around the edges, use a spatula to push them up as close to the cauliflower as possible.
Bake for 40-45 minutes until knife tender. Let cool for 5-10 minutes before slicing into wedges and serving.