Risotto Con Pesce Gatto E Erba Cipollina

• 1 celery stalk
• 1 fish
• 1 cipollotto
• 1/2 lemon
• 1/2 carrot
• 1/2 head fennel
• 1/2 onion
• 375 gr catfish fillets
• 130 gr vialone nano rice-see recipe
• 40 gr butter (unsalted)