Mix water and yeast and let stand 15 minutes. Gradually pour in 2 cups of the flour mixture and to incorporate. Mix for about 1 minute to form a sponge. Let stand, covered for at least an hour. Put sponge in the bowl of a standing electric mixer. Using the dough hook, add the salt and oil, then flour 1/2 cup at a time to form a dough. Remove from bowl and knead until smooth for approximately 7 minutes. Place in a clean oiled bowl and let rise, slowly, about 2 1/2 hours. Divide dough into 4 balls, let rise again for 1/2 hour and roll out into a freeform rectangle about 1/4-inch thick. Preheat oven to 450 degrees F. Lightly oil a baking sheet, place the dough on the sheet and prick the surface with a fork. Bake for 10 to 12 minutes until lightly golden brown.
Place all ingredients in a food processor and process until smooth.
Spread each flatbread with a few tablespoons of the pesto. Top the pesto with the merguez, ramps, manchego and tomatoes. Season with freshly ground black pepper. Place the flat bread back in the oven and bake for 5 minutes to heat through.
Remove the flatbreads from the grill and sprinkle with Parmigiano-Reggiano.
To oven roast tomatoes - slice plum tomatoes in half, lengthwise, brush with oil and season with salt and pepper. Place in a 300 degree oven on a baking sheet and bake for 45 minutes