For the Smoky Romesco Sauce
Toast all ingredients, purée together, set aside.
For the Cauliflower Croquettes
Heat oven to 400°F. Place cauliflower on baking sheet and bake for 15-20 minutes. Set aside to cool.
Heat oil in large frying pan over medium heat and stir in flour. Whisk mixture for 5 minutes. Slowly pour in milk and whisk continuously until mixture thickens, approximately 20 minutes. Add cheese and stir until melted, then add cooked cauliflower.
Pour mixture into a bowl and cover with plastic wrap until cooled. Shape cauliflower mixture into desired circular shape, place on baking tray and freeze for 10 minutes.
Place breadcrumbs and eggs into separate bowls and dip each cauliflower croquette into the egg and then cover in breadcrumbs. Bake for 25 minutes at 400°F, then grill for 2 minutes, until golden.
Spoon Romesco sauce on top of cauliflower croquette and garnish with hazelnuts and oil.