Follow these detailed steps to create flawless mini waffle sandwiches every time. The process is best broken down into preparing the components first and then assembling them for the perfect warm, melty finish.

Step 1: Prepare the Waffle Batter

1. Combine Dry Ingredients: In a large mixing bowl, add the all-purpose flour, granulated sugar, baking powder, and salt. Use a whisk to mix these ingredients together thoroughly for about 30 seconds. This step is vital as it ensures the baking powder is evenly distributed, which leads to a consistent rise and a uniformly fluffy texture in every waffle.
2. Combine Wet Ingredients: In a separate medium-sized bowl, crack the two large eggs and whisk them lightly. Pour in the whole milk and the vanilla extract, and whisk again until everything is just combined.
3. Melt the Butter: Melt the stick of unsalted butter in a small saucepan over low heat or in a microwave-safe bowl. Set it aside to cool slightly for a minute or two. This is important because adding piping hot butter to the egg mixture can cause the eggs to scramble.
4. Mix Batter: Pour the wet ingredient mixture into the large bowl with the dry ingredients. Gently fold them together with a spatula or wooden spoon until they are just combined. A few lumps are perfectly okay! Overmixing the batter develops the gluten in the flour, which will result in tough, chewy waffles instead of light and fluffy ones.
5. Incorporate the Butter: Slowly drizzle the slightly cooled melted butter into the batter while continuing to gently fold. Mix only until the butter is incorporated. The batter should be relatively thick but pourable. Let the batter rest for 5-10 minutes while you prepare the fillings. This resting period allows the gluten to relax and the flour to hydrate fully, leading to a more tender waffle.

Step 2: Cook the Savory Fillings

1. Cook the Ground Beef: Place a medium skillet over medium-high heat and add the olive oil. Once shimmering, add the lean ground beef. Break it apart with a spatula and cook until it is browned all over, about 5-7 minutes. Season generously with salt and pepper. Once cooked, drain any excess fat and set the beef aside in a bowl.
2. Wilt the Spinach: In the same skillet, add the fresh spinach. Cook, stirring occasionally, until it has wilted down completely, which should only take about 1-2 minutes. Remove the spinach from the skillet and set it aside. Squeeze out any excess moisture if necessary.
3. Scramble the Eggs: In a clean bowl, crack the 6 large eggs and season with a pinch of salt and pepper. Whisk vigorously until the yolks and whites are fully combined and slightly frothy. Reduce the skillet heat to medium-low. Pour the egg mixture into the skillet and cook, gently pushing the eggs from the edges toward the center with a spatula, until they are soft and fluffy curds. Avoid overcooking them, as they will cook a little more during the final assembly. Set the scrambled eggs aside.

Step 3: Cook the Mini Waffles

1. Preheat the Waffle Iron: Plug in your mini waffle iron and allow it to preheat completely. Most models have an indicator light that will turn on or off when it’s ready. A fully heated iron is the secret to a crispy exterior and a quick cooking time.
2. Cook the Waffles: Lightly grease the top and bottom plates of the mini waffle iron with non-stick cooking spray or a light brush of melted butter. Pour about 2-3 tablespoons of batter into the center of the iron (the amount will vary slightly depending on your specific model). Close the lid and cook for 3-5 minutes, or until the waffle is golden brown and crisp. The steam will subside significantly when the waffle is done.
3. Keep Waffles Warm and Crispy: As you cook the waffles, do not stack them on a plate, as the trapped steam will make them soft. Instead, place them in a single layer on a wire cooling rack. To keep them warm and crispy while you cook the entire batch, you can place the wire rack on a baking sheet in a preheated oven at 200°F (95°C). Repeat the process until all the batter is used.

Step 4: Assemble the Mini Waffle Sandwiches

1. Layer the Ingredients: Take one warm mini waffle and place it on your work surface. Sprinkle a small amount of shredded cheddar cheese on top.
2. Add the Fillings: On top of the cheese, layer a small spoonful of the cooked ground beef, a folded slice of ham, a bit of the scrambled egg, and a few pieces of wilted spinach.
3. Top it Off: Sprinkle another layer of shredded cheddar cheese over the fillings. This second layer of cheese acts as a delicious “glue” that will melt and hold the top waffle in place.
4. Complete the Sandwich: Place a second mini waffle on top and press down gently.
5. Melt and Serve: For the ultimate gooey, melted experience, you can place the assembled mini sandwiches back into the closed (but turned off) waffle iron for about 30-60 seconds to melt the cheese. Alternatively, place them on a baking sheet and pop them into the 200°F oven for a few minutes until the cheese is perfectly melted. Serve immediately.