Season 260g minced meat with salt and pepper, add 2 teaspoons bourbon whiskey. Form into 2 patties and refrigerate until ready to grill.
Cut 2 onions into rings and 1 red pepper into cubes. Heat a piece of butter in a pan over medium heat. Sauté onions and peppers for 5-7 minutes until softened. Add brown sugar and salt, cook for 2-3 minutes until caramelized.
Melt 150g Gouda in a saucepan over medium heat. Cut 1 green pepper into cubes and add with some jalapeños. Stir in some cream until the sauce reaches a pourable consistency.
Grill 2 burger patties over medium-high heat for 3-4 minutes per side until they reach 71°C / 160°F internally. Lightly toast burger buns on the grill for about 1 minute.
Brush bottom halves of buns with mustard mayonnaise. Layer with caramelized onion-pepper mixture, burger patty, gouda cheese sauce, and some spinach. Cover with top halves of buns and serve.