Mushrooms:

6 oz Baby Portabella Caps (should be six mushrooms), cleaned and stems removed (reserve stems for stuffing mixture).

Stuffing / Filling:

6 Mushroom Stems
1 Medium Sweet Onion
1 Garlic Clove
8 Oz Sliced Water Chestnuts, rinsed and drained
2 Oz Finely-Diced Prosciutto
1 Egg, beaten
1/8 Teaspoon Salt
1/8 Teaspoon Ground Black Pepper

Note: for simplicity, I bought my Prosciutto pre-diced in a small 4 oz container.

Sauce:

¼ Cup Ketchup
2 Tablespoons Packed Brown Sugar
1 Tablespoon Wheat-Free Tamari
1 Tablespoon Honey
Several Drops of Tabasco sauce (optional)

Wash mushrooms and remove stems. Place stems in a food processor. Coat a Pyrex baking dish with cooking spray; add washed mushrooms.
Place onion and garlic in food processor with mushroom stems and blend. Add water chestnuts and lightly blend (leaving larger chunks). Add beaten egg and Prosciutto, salt and pepper, stir (do not blend in food processor). Mound stuffing into each mushroom cap. Extra stuffing can be spread around the bottom of the Pyrex dish.
In bowl, combine all sauce ingredients; mix. Divide sauce over top of mushroom caps.
Bake in 375° oven for 50 minutes. Remove from oven and enjoy!