In a medium bowl, mix together the flour, salt and yeast. Add the water and mix with a wooden spoon or your hands. It should be sticky, but not lumpy.
Cover with saran wrap and a towel in a warm place, allowing it to rise for 24 hours. Transfer to a floured surface and shape into ball. Use when ready.
Sauce
Add butter to small skillet over medium heat. Add garlic and cook for 30 seconds. Add flour and cook for about 1 minute, or until bubbly.
Slowly whisk in milk and chicken stock and cook for about 1 minute or until thickened. Add ¼ cup Parmesan cheese and and crushed red pepper flakes, stirring to combine. Remove from heat and set aside.
Pizza
Preheat oven to 500°F. Lightly oil a 10x15 sheet pan. With oiled hands, gently stretch the dough across length and width just past the edge of the baking sheet in an even layer. Set aside.
Heat medium skillet with 1 tablespoon olive oil over medium-high heat. Season steak with salt and pepper and cook for 1-2 minutes on each side until cooked. Remove from skillet.
In same skillet over medium-high heat, add remaining olive oil. Add sliced peppers and onion and and cook for about 3 minutes.
Spread a light layer of the sauce over the dough, leaving about 1 inch around the edges untouched. Spread the cooked steak, peppers and onion throughout the pizza. Top with the cheese.
Place in the oven and bake for 10 minutes, rotate the pizza, and bake another 3-5 minutes or until the crust is golden and the cheese has melted.