1. Place squash slices with enough water to cover in a 4-quart saucepan.  Heat over medium heat, bring to a boil and continue boiling for 5 minutes or until squash slices are tender. Drain and set aside.
2. Separate egg whites from yolks.  Place whites in the bowl of a large mixing bowl.  Beat until soft peaks form.  Add yolks, mix on medium speed for 10 seconds. Add 1 tablespoon flour. Continue mixing until thoroughly combined. Mixture should be thick and creamy.
3. Slice panela cheese slices in 1-inch squares.  Sandwich each cheese square between two squash slices, keeping the squash slices consistent in size.
4. Heat oil in a frying pan over medium heat.
5. Place remaining flour in a shallow bowl. One at a time, gently cover each squash/cheese set with flour evenly on all sides.  Gently shake excess flour. Dip into batter holding squash slices between fingers to keep cheese from falling out. Place in hot oil and carefully baste with spoonfuls of hot oil until golden brown.  Remove from oil and place on a paper-towel-lined plate to soak up excess oil.  Repeat with remaining squash/cheese sets. Serve warm with tomato caldillo or your favorite sauce. 

Directions for Tomato Caldillo

1. Heat 2 tablespoons oil in large pan over medium heat, add tomato halves, onion strips and garlic.  Cook for 10 minutes turning tomato halves, onion strips and garlic frequently with tongs; do not burn. Tomatoes should be soft and skins should begin to peel.
2. Add sautéed tomatoes, onion and garlic to blender container.  Add 2 cups water and blend until smooth.  Transfer blended mixture back to pan and heat over high heat, season with salt and oregano, bring to a boil and reduce heat to medium.  Simmer for 5 minutes. Set aside and keep warm.