In a large pot over medium-high heat, bring stock to a boil.
Slowly pour in polenta, stirring with a whisk as you add it. After all polenta is added it will take about 2 minutes for it to begin to thicken. Reduce heat to low and continue cooking and stirring occasionally for approximately 40 minutes, or until polenta is smooth, and no longer gritty on the tongue. Just before finishing, stir in Parmigiano-Reggiano and thyme.
In a 9 by 12-inch baking dish, add 1 tablespoon water. Transfer polenta to baking dish and spread until it is of uniform thickness. Refrigerate for 1 hour, or until it solidifies.
To make roasted red bell pepper sauce, roast the red and poblano peppers whole over a gas flame, a charcoal flame or under a broiler, turning 1/4 rotation every few minutes, until entirely blackened. Immediately place in a paper bag, seal, and let sit for 3 minutes. Peel off the charred skin and discard. Slice the peeled peppers open and discard the membranes and seeds
In a saute pan over medium heat, heat the butter and add the shallots. Cook for about 6 minutes, stirring frequently, or until the shallots just begin to show signs of browning.
Add the stock, 2 roasted bell peppers, poblano chili, and thyme. Bring to a boil, then immediately reduce heat to medium-low and simmer for 15 minutes. (Adjust heat as required to simmer.)
Remove from heat and let cool. In a food processor or blender, add pan contents along with the remaining red peppers, lemon juice, salt, and pepper. Blend until smooth. Reserve.
Use a cookie cutter or a pairing knife to cut out desired polenta shapes. In a saute pan over medium high heat, add oil and saute polenta shapes for approximately 5 minutes per side, or until a golden brown crispy crust has formed on each side.
Just before serving, re-heat sauce in a saucepan and stir in cream. Ladle 2/3 cup of roasted red bell pepper sauce into a shallow bowl. Top with one piece of polenta. Serve immediately.