Do you have a secret recipe you'd protect with your life?

What's a dish you cook that everyone loves but you'll never share how you make it, even to your best friends?

Recently, I've been making this marinade for fish and occasionally chicken that slaps. I made it up on my own and spent a few months perfecting the spice blend. Now, when I make it all the time, my friends and family always ask for the recipe. But I want it to be my thing, my recipe. Maybe one day I'll share it but for now, it's like a little culinary trophy for myself. And I'm not telling anyone.