Bring a pot of water to a boil and add a small handful of salt. Add gnocchi to boiling water and cook until they float to the surface. Remove and set aside.
Meanwhile, heat a deep skillet to medium heat. Lightly oil pan and cook ham steak (4-5 minutes per side). Remove from pan and dice.
In the same pan, melt butter and saute garlic and shallot until fragrant (about 1 minute). Whisk in flour until incorporated to form a paste. Slowly add the milk to mixture, stirring constantly until thickened. Stir in dijon mustard and thyme. Bring the mixture to a gentle simmer. Season with salt and pepper. Add the cheeses and stir until melted. Stir in ham, gnocchi, and 3/4 cup of peas.
Transfer mixture to a shallow baking dish. Top with remaining 1/4 cup of peas and breadcrumbs if desired. Bake 18-20 minutes or until bubbling.
Remove dish from oven and sprinkle with chopped fresh parsley.